my computer starts with C prompt with groove.exe running(2 posts)
groove.exe is part of an Office sharing tool. Unless you really need it disable it or remove it. It is a resource hog as well.
Boot your machine into safe mode and see if you can get into windows.
At the command prompt type; msconfig then press enter
Now disable it in the 'startup' tab
Reboot into windows. If you want to remove you will need the install disk