Agree with Gandalf. Quite likely a virus if you're having the same problem with regedit and msconfig.
Try Task Manager too to see if it suffers from the same problem.
Do a virus scan and hope it can sort it out for you.
In the meantime, if you need to use any of these applications, try making a copy of each of the exe files and renaming the copy with a .com file extension.
REGEDIT should be in C:\WINDOWS\REGEDIT.EXE.
msconfig.exe should be in C:\WINDOWS\pchealth\helpctr\binaries\msconfig.exe
Task Manager should be C:\WINDOWS\system32\taskmgr.exe
Make a copy of each of them in their own folder, and rename the copy to regedit.com and so on. Then double click the .com file to use the application. These applications may also be needed in getting rid of the virus itself if the antivirus doesn't pick it up.