Avast scanning takes forever just scanning a total of 4.66 GB of data on hard drive 2hours. Quick scan is perfect though and quick. Boot time scan is quicker and better if you need to do this. Is the scan engine going to be improved and faster on next program update? as normal scan uses 100% CPU LOAD AND MAKES THE COMPUTER UNUSEABLE!!! :o
What are the specs of your system?
IBM 600e, Pentium 2. 400mhz 356MB Ram MAXED OUT! Xp Sp3.
Under Avast 4.8 full scan only took 35 mins at least and on maximum scanning archives and did not use much CPU usage while scanning peaking around 70% and the computer was useable. I know my computer is not fast though for todays standards but is a good old workhorse had this from new first running Win 95 & Win 98 & Xp after.
Will be thinking to go back to Avast 4.8 as 5 is too buggy at the moment as this was solid antivirus. 
avast! 5 is fast, especially on repeated scans. But you answered yourself with the specs. Your system is really prehistoric and i doubt that avast! 4.8 was any faster on it. More slower than faster.
I found avast 5 normal scan rather faster than avast 4.8. But just don’t know on older machines, and I think we don’t need normal scan so often while we can choose quick scan for weekly scanning.
Way too little memory…its a wonder that it runs as well as it reportly does. I have a Dimension 8400 that has 1 GB which to me is the minimum needed for XP.
On the first full scan it took about an hour and 25 minutes to scan about 39 GB of data. Thanks to the “persistence” feature the follow up full scan took only 25 minutes.
400 MHz? :o Wow, it’s been a while.
Yeah, just stick with 4.8 for as long as you can if it’s causing too much lag.
That’s rather strange, avast! 5 should be faster (and use less memory) than avast! 4.x.
Is it the AvastSvc.exe process that is using all the CPU, or is there any other?
AvastSvc.exe was using all the cpu through task manager on normal scan. (Version 4.8 ran alot less around 70% varible peaks on graph through task manager set on thourough with archives.)
Version 5. Quick basic scan was good & fast took 10 mins. Tried shedule boot time scan was quick around 45mins or so.
Had major problems updating definitions, went back to V4.8 and tried to re install V5 again on top of V4.8. Finally updates now working and appears to be stable.
I think re installing has cured my 100% cpu problem. AvastSvc. running 20% See how it goes while doing a full scan
Nope later 100% CPU Again AvastUI.EXE RUNNING 50% AvastSvc Running 50% taking all cpu now and then up and down like a yo yo!