Task Manager Problem

The file change uxtheme.dll could cause your task manager to dissappear
uxtheme.dll which protects the system from third party themes.

and i see replacer (Replacer is an easy to use system file replacer for Windows 2000 and XP. It safely replaces protected or in-use system files. ) running in the task manager.

try changing the theme or do a system restore.It looks like the theme and replace caused the problem

http://www3.telus.net/_/replacer/

http://themes.belchfire.net/index.php?showtopic=9001

http://www.ghacks.net/2008/05/04/windows-xp-service-pack-3-uxthemedll-patch/