Outlook 2000 Closes Automatically After Openning

Hello Everyone,
System Specifications:
Windows XP Media Center Edition 2005
Office 2000 Premium
Anti virus: Avast Home

Problem:
This is a friend's computer. Everything was working OK, then since this
weekend when he tries to open outlook, it opens, shows the inbox, and then
closes without any message.

The computer had a spyware that I removed successfully.

I tried the following and the problem persists:
1) Reinstalling office
2) Repairing Outlook
3) Unistalling and reinstalling the Avast anti virus
4) Removing and then creating again the email account

Some times (without me knowing why) the outlook opens and works for a while,
then the problems appears again. Outlook opens and then closes automatically
without messages.

I do not know what else to do, any help is greatly appreciated.

Thanks in advance,
Freddy