Task Manager Damaged?

I have a Windows Pro 2000 user with a damaged Task Manager. When started, it comes up in the system tray and a minimized button appears in the task bar with no text. If you try to maximize it nothing happens, making it completely useless. I tried replacing taskmgr.exe with no luck. I suspect this may have been the result of a virus or file corruption but have not been able to find info on what other files taskmgr.exe depends on so I can replace them. Thanks for any help on this!