Ask questions about dedicated servers here and we and other users will do our best to answer them. Please also refer to the self-help section for tutorials and answers to the most commonly asked questions.
Sometimes when Windows does this you just need to restart again. Does that option work in this case?
Otherwise, your Windows install may have become corrupted somehow (one of your applications may have deleted a critical file, or a Windows update may have failed, for instance). You may need to recover your customized files and reinstall it. We write about how to recover files here: viewtopic.php?f=46&t=10584