start up problems

I have windows 2000 when it starts up I receive a message saying a required.DLL file.C:\Windows\System\ImageHLP.DLL.was not found.Then when I try to acess my documents or my computer or search for files,it comes up with a message saying,explorer hascaused an error in QCBAR.DLL AND WILL NOW CLOSE .what can be done to fix this problem?