Recently, I had a slowdown at my IE 9. I found the reason as the temporary files produced by Avast, at the %temp%, Low, avast folder. Well I like surfing, and there were 850,000 files there, deposited nearly in one month, and it required hours for deleting! :-[ Now I can surf as quickly as before! Is there a way of preventing such a build of temporary files? Is such a huge number of temporary files required for Avast to work? I deleted them 2 days ago, and they are already 35000 now! :-\
The unp99999999.tmp files in the c:\windows\temp_avast_\ folder (is where avast unpacks/sends copies of files to be scanned) are placed there by avast so that they can be scanned, on successful completion of the scan that folder should cleared with exception to the webshlock.txt file.
So clearly there is something wrong on your installation, something blocking the clearing/scanning of files in that folder.
Have (or did) you another Anti-Virus installed in this system, if so what was it and how did you get rid of it ?
What other security based software do you have installed (and are they resident), anti-spyware/malware applications, etc. ?
" The unp99999999.tmp files in the c:\windows\temp_avast_\ folder (is where avast unpacks/sends copies of files to be scanned) "… The avast folder at " temp " seems completely empty. The avast temporary files are gathered at " temp\Low_avast_ folder! The full correct path is; AppData\Local\Temp\Low_avast_ …
I reinstalled already, and 35000 temp files in just two days! I have resident Comodo, Spybot Search and Destroy, no other anti-virus and I did not try any. Sometimes I full scan with Malwarebytes Anti Malware or Windows Defender. And I could not see " webshlock.txt " file there, in both avast files? I am using windows 7, 64 Bit.
I have been using Avast free since nearly 5 years, mostly together with the Comodo and Spybot. I never had such a problem. I think everything started at most one or one and a half month ago. But I do not have the slightest idea why?
The webshlock.txt is only there when you are browsing and the web shield is active.
Reinstalling isn’t going to resolve it if there is any conflict from another security application blocking the removal of the files in that folder.
I specifically asked about resident security applications, if MBAM isn’t MBAM Pro it is unlikely to be that ?
I would advise you exclude the AppData\Local\Temp\Low_avast_ from windows defender which is resident. I don’t know how you have this AppData\Local\Temp\Low_avast_ as the avast temporary folder as the one I mentioned is the default location. Presumably you have changed your environment variables for the Temp folder location ?
This strange Temp location may be the cause of the failure to empty it.
Just for info…I have this folder, but it is empty…
I have:
Appdata\temp_avast_ ← Empty
Appdata\temp\low_avast_ ← Empty
C:\Windows\Temp_avast_ <-This is the one that is used, and contains webshlock.txt
Thank you for clear information about pathways spg SCOTT; 
Sorry, for some misinformation, the correct ones are written below;
Appdata\temp_avast_ ← This folder is empty at my computer!
Appdata\temp\low_avast_ ← This folder is full with unp…tmp files and their number is increasing steadily.
C:\Windows\Temp_avast_ I have this folder with webhlock.txt, and nothing else.
I do not think that I have changed the place of any temp folder, at least knowingly.
In the last 3-4 days I have performed chkdsk twice.
I excluded C:\Windows\Temp_avast_ from Windows Defender but nothing changed.
No, it is not MBAM Pro, I am using free version for making monthly scans only.
Check your environment variables and change the Temp location to c:\Windows\Temp\ that should then force avast to use the c:\windows\temp_avast_ folder to unpack/scan/remove the files from that folder.
Though I’m at a loss as to why the webshlock.txt file is in there and no files. So I would also guess that the webshlock.txt isn’t present in your Appdata\temp\low_avast_ folder.
I’m not too surprised nothing happened with your exclusion in windows defender as there are no files in there, as you say they are in the Appdata\temp\low_avast_ so that would be the folder to exclude.
Though I would say that you should consider changing the Temp environment variable.
Thank you for your help DavidR, I will try to change the Temp environment variable, but I am not an expert and it will take a few days.
Just use the windows Help & Support feature in your OS and type in Environment and that should pull up all the information you need to do this, see image extract (which is on my XP system, will differ for your OS).
Usually you can access this from Control Panel, System, Advanced System Settings, in my win7 system this is shown as:
Variable - TEMP
Value - %USERPROFILE%\AppData\Local\Temp
This uses the c:\windows\temp folder as the Temp environment variable and avast uses the c:\windows\temp_avast_ folder.
Ok, below is the latest situation! ???
I reinstalled Avast free edition again and as you have said it did not solve my problem, I have these now;
C:\Windows\Temp_avast_ Contains webshlock.txt…And there are some other files in Temp folder like hp files etc. too.
Appdata\temp_avast_ ← Empty
Appdata\temp\low_avast_ ← Still full of unp…tmp files.
In the Environment Variables I have two variables;
1.st one is;
Variable - TEMP
Value - %USERPROFILE%\AppData\Local\Temp
2.nd one is;
Variable - TMP
Value - %USERPROFILE%\AppData\Local\Temp
I now changed TEMP variable’s Value to " C:\Windows\Temp " …hope it will work, I must test a few minutes! :-\
I hope so too as this has been a weird one.
Sorry DavidR, no use: Still it is producing files, at somewhere else.
Now the situation is;
C:\Windows\Temp_avast_ Contains webshlock.txt. No other file in avast folder.
Appdata\local\temp_avast_ ← Empty
Appdata\local\temp\low_avast_ ← Still full of unp…tmp files.
Yes, and I do not know the slightest idea how this happened? 
I am not “the owner of the absolute truth”, so I’m going to say this from a humble position, and I might be wrong.
I think you are “playing with fire” here. The defaults for TEMP and TMP are the ones you HAD.
For a clean complete uninstallation of Avast, you need to run the specific removal tool from Windows Safe Mode, indicating in the removal tool the correct installation folder and version(s). You need to reboot into Safe Mode for each version of Avast you ever had, so to really remove all relevant remnants.
Before reinstalling, you can delete all temporal files / folders related to Avast, manually and under Safe Mode if possible.
Then you need to download anew the latest stable setup.exe for Avast, install as administrator (right-click → “Run as Administrator”) and reboot immediately after the installation finished (no testing, no checking, no scanning, “nada” before reboot).
Whichever the reason for the old temp folders of Avast, or the current accumulation of “too many” temporal/older files related to Avast, I seriously doubt that changing the traditional TEMP folders is the solution. It might had been, if it was the other way around (using TEMP folders other than the traditional).
Of course, this is your system and you are free to try whatever you want.
ady4um, yes the system is my system, and so I changed everything to default, I uninstalled Avast with utility, ( and spybot and comodo and MBAM etc. ) very strictly doing what you have said. But nothing changed.
There are also removal utilities for other security tools that you may think that you uninstalled. Some (but not all) of them are found at http://thewebatom.net/uninstallers/security-software/.
What I was trying to say is that, if you already have the default paths of TEMP/TMP (as it seems you had before you changed it), then those paths shouldn’t be the reason for those temporal files, hence, why change it?
When you say “nothing changed”, let me ask you specifically: after uninstalling all those tools (including Avast), have you deleted all those temporal files manually under Safe Mode, before reinstalling Avast under Normal Mode?
And to be clear, temporal files ARE created. The only problem would be if Avast is unable to delete them once in a while (BTW I don’t know if the deletion frequency is constant). The creation (and deletion) frequency depends on the updates of Avast (which are sometimes more “partial” with less KB to download, and sometimes more “complete”).
Thank you for the removal utility page, ady4um, will use in the future!
And yes I cleaned all the tmp files before reinstallation manually in the safe mode, I even cleaned the registry manually, for the word " Avast".
I think best will be a new system installation in a short time, and until that manually cleaning the tmp files from time to time.
If you have enough space, then I would try leaving it “as-is”. Windows itself also partially works like this, automatically cleaning some areas only when “really” needed.
By “letting it be”, you could also test this Avast temporal files/folders during and up to, say, 40 days, to check if either the number or the total size is still increasing, or it has stabilized in a certain value (more or less).
It may well be “just annoying but nothing to really worry about”.
Yes, I will leave it as it is. But as I mentioned in my first message, ( when I understood the problem because of the slowing at IE, the number of files were 850000! ) it takes a long time to delete after such a build up of files. I will delete them in every two weeks at most. And I will watch the situation, as DavidR mentioned this is a very weird problem.
Thank you for your help DavidR and ady4um.
This is interesting…
Just got an alert in this location…
08/10/2011 16:55:47 C:\Users\Scott\AppData\Local\Temp\Low\_avast_\unp208123638.tmp [L] HTML:Iframe-inf (0)
File was successfully moved to chest...
FileSystemShield alerted. On what should have been a webshield alert…weird…
(I say webshield because it is a website that is causing this alert.)
Well I still think that there an issue with the temp variables, since the webshlock.txt file as far as I’m aware would have to be in the folder in which the files should be.
If webshlock.txt file isn’t in that folder then I guess any files sent there aren’t being scanned by the web shield, that would also follow that the folder wouldn’t be cleared and why the subsequent detection by the File System Shield on a file that essentially shouldn’t be there.
Definitely weird.