Too much scanning!

Avast Free Antivirus / Premium Security
1

About my computer:

Operating system: Windows XP Professional SP 2
Avast 4.8 Home Edition
VPS 090905
Celeron 2,26 GH 480 MB Ram
Internet: Direct through DSL
Webmail: G-mail
No other security software

TWO PROBLEMS:

  1. AVAST scans, re-scans, and rescans, and rescans, and rescans… and rescans ad infinitum every file, program, etc. I open at every time, even if I just closed the same half a minute before, and without any changes to the file. THIS UNNECESSARY RESCANNING SLOWS DOWN THE COMPUTER to the point where I rather close AVAST and remain unprotected. THIS IS A MAJOR BUG IN AVAST!!!
  2. “Morning Sickness”. When I first boot the computer every day, some program takes over the hard drive for about 10 minutes. I suspect that it maybe either AVAST doing a boot scan, though I do not have it set to do one, or maybe there is a virus or similar that gotten past AVAST and has turned my computer into a “zombie” that is being used to send out spam.

Any suggestions?

2

Pretty much all antiviruses scan same file forever if it’s accessed. Only few check if it was modified in between.

As for the startup, it’s common for PC to have hiccups untuil its fully ready. Especially if you don’t have loads of RAM, fast disk drives and fast CPU. Even after you see the desktop, Windows are still loading and starting services and other stuff.
You’ll have to test that by yourself to see if avast! is really reason for that. Disable it and set to persist changes after system restart. Check if anything changes on next few system boots.

For the file that is continuously scanned, check where it is located and post the full path here (path plus filename and extension).

3

it’s normal that avast is scanning the accessed/used files. you didn’t mention if you have the default settings of avast. because you can set it up to scan every file (no matter the extension). you also didn’t say if your windows firewall is on. 480 MB of RAM is not much theese days, but it should be enough. and it depends how many programs you have in start-up. if really takes 10 minute to start up, you might have a problem there.
you can check in the task manager, right after loging into windows, which proccess is consuming the CPU.

4

Which was your old antivirus before avast?
Which is your Standard Shield sensitivity level?