i can not start avast home

hi
i have a problem with avast 4 home edition; i had a virus and i got rid of it but now i can not start avast. i see the ‘a’ blue ball in the system tray but when i click on start avast nothing happens.
can u help me?

Which is your Windows? 98, Me, XP?
Do you use any other antivirus in your computer?

Can you try to repair your installation?
Go to Control Panel > Add/Remove programs > avast! antivirus > Remove. Then choose Repair function in the popup window (Repair). You must be connected to the internet while repairing.

If this does not help, can you uninstall / boot / install / boot again?

windows xp
i 've tried repairing but no luck
i have also reinstaled the program but the problem didn’t solve

Please, post the last 50-100 files of avast log files:
C:\Program Files\Alwil Software\Avast4\DATA\log\Setup.log
C:\Program Files\Alwil Software\Avast4\Setup\setup.log