task manager fails to open

Today I returned to my Windows XP computer to find that another user was still logged on. I logged onto my side and attempted to open the task manager to log him off. Unfortunately, I recieved no response when I pressed CTRL-ALT-DELETE. I then went to Start->Run and tried to open taskmgr from there, however, I recieved this 'Taskmgr' error: "Another program is currently using this file."

I restarted the computer to log off the other user, and tried to open the task manager again both ways, however, I still had the same problems. I scanned the computer with Ad-Aware SE, Spybot - S&D, and the Microsoft Anti-Spyware Beta (as well as a small Microsoft program that looks for well known viruses), and cleaned it with CCleaner. I then restarted and the problem still plagued me.

What could be causing this error?

--thanks!

p.s. - I don't use Panda Software as the last version messed with my system and still cannot be removed entirely.

 

Have you tried logging on to all of your user accounts and logging them off one-by-one? Honestly, I don't know how other users being logged on would disable your TaskManager unless maybe you have a highjacker/trojan. And yes, I know that you ran some scans but it is better to post a HJT log because there is malware that erases it's own tracks (keyloggers I think).

See if system restore works for you, and if not try a sfc /scannow to check all of your system files.

sfc /scannow instructions:
1. Put your XP CD in the tray and when setup begins press ENTER.
2. Close all open applications and such.
3. Start > Run > (type) cmd > (type) sfc /scannow (there is a space after sfc) > click ENTER
4. Now just let it do it's job. When it is finished you can type EXIT then press ENTER.
5. Reboot because it makes your machine happy. : )