I Alt-Ctrl_Del but no task manager appears and no shutdown option.

What I do get is a box with the following headers on the top:
user:id:status:client name:session
Owner is shown under User
ID is 0
Status is active
Client name is blank
session is console.
If I right click owner I get a menu saying disconnect or logoff
If owner is just selected, then at the bottom of the box I can choose disconnect or logoff.

But no task manager.

What can I do to retrieve it?

Updated Virus checker shows no infection.

using winXP home pack 2

John

If you have Windows XP configured to use the Welcome screen, this can happen.
Try disabling the Welcome screen and see if this solves the problem.