Go to 'start\run\. Then type exactly the following 'taskmgr.exe' make sure you type the exe so it can bypass any unwanted .com files if any exist attached to it. Tell me if it works when you put in the exe.
are there any strange looking files on your desktop? I ran into this problem a few days ago on XP. The files created prevented Task Manager to be opened, and I had to go in with Safe Mode to get rid of the files.
hmm i have a bug called install "winfixer 2005" that puts itself on my desktop every time but ive had it for a while and the task mgr just recently stopped working.