Unable to open taskman says it is being used by another file?

Just make sure that your anti-virus virus definition is up-to-date, run a full scan and if you find any worm/virus delete it.

Taskman? You mean task manager?

Did you try rebooting? If that doesn't help, try using System Restore.

I'm not sure how windows opens it, but you could go to the run line and try typing taskmgr.exe

When does it say that the file is in use? Do you press ctrl+alt+del to try to get to it?