This seems like a job for essexboy
Started getting problems on startup a while ago. Usually I got out of this rut by restoring to an earlier point, but now there are no more of these available (!). I read about this problem on the forums, here is what the scan revealed (attachment):
Thank you for your work, all the best !
As essexboy lives in UK its 1am here.
Please check back tomorrow and follow his instructions. 
Download the attached fixlist.txt to the same location as FRST
Run FRST as before and press fix
On completion try a normal boot
Hello, thank you for the quick response. Sad to say the problem has not yet disappeared. Safemode boot still hangs at aswrvrt, normal boot still shows BSOD fatal error c000021a. Attached is the fixlog. Thank you for taking the time.
The BSOD indicates an integrity problem with windows… Lets see if this works
Download the attached fixlist.txt to the same location as FRST
Run FRST and press fix
Try again to boot
Still nothing, sorry. When attempting to boot in safe mode the driver < CLASSPNP.SYS> now hangs.
It looks like a hard drive problem, the one possible option remaining is to run a chkdsk
Are you able to get to the command prompt in the recovery console ?
Select Command prompt
http://i1224.photobucket.com/albums/ee362/Essexboy3/RepairVista_7277.jpg
Type :
chkdsk c: /r
Once completed try a reboot
Yes, the prompt works fine. Chkdsk is ongoing.
Chkdsk found no problems, BSOD same as ever when booting. What does this mean? Hardware related?
Also, I tried to input the command " bootrec /rebuildbcd ". It says :“Total identified Windows installations: 0”
Yes, I am afraid it is more probably a severe windows corruption or a HDD error that chkdsk did not catch
It may be time to re-install windows I am afraid. Do you have a windows image or do you need a way to back up you important files etc…
Very well, thank you for all your help. The notebook (HP pavillion) has a run-in test which showed no errors on memory or hard drive. How could I backup my files now, using linux or something ? Is it possible?
How did this problem start out as something avast related, only to then enter the realm of insolvable OS errors? I suppose it is a fault of avast’s integration with windows, as it only appeared after a reinstall of avast coupled with an ordinary windows update. It is definitely a software issue and one with serious implications.
Started getting problems on startup a while ago. Usually I got out of this rut by restoring to an earlier point, but now there are no more of these available (!).I was basing my responses on this :)
As it stands Avast is no longer active on your system, all services and drivers have been deleted
Download Peazip to the desktop
Run and install the programme
As it installs this page will show, deselect the AVG ticks
Press decline and it will then install cleanly
https://dl.dropbox.com/u/73555776/peazip.jpg
Download the following files to the desktop … Right click the links and select save as…then select desktop
Right click OTLPE on your desktop and select …Open as archive
https://dl.dropbox.com/u/73555776/Unzup%20archive.png
Select OTLPE standard
https://dl.dropbox.com/u/73555776/select%20archive.PNG
Click Extract, ensure that desktop is selected
https://dl.dropbox.com/u/73555776/extract%20archive.PNG
Insert the USB stick Then run Rufus
https://dl.dropbox.com/u/73555776/rufus.JPG
Select the ISO file on the desktop via the ISO icon.
Press Start Burn
https://dl.dropbox.com/u/73555776/RufusISO.JPG
Once the USB has burnt then
[*]Reboot your system using the boot USB you just created.
Note : If you do not know how to set your computer to boot from USB follow the steps here
[]As the Programme needs to detect your hardware and load the operating system, I would recommend a nice cup of tea whilst it loads
[]Your system should now display a Reatogo desktop.
[*]From this standard XP interface you will be able to backup your data
i took the shorter route of moving some of the important stuff by way of notepad in command prompt. thanks for all the help. you’re a great unsung hero, my friend !
I am sorry we could not resolve this problem