This is probably a corrupted MBR partition on your drive and many things can cause this such as, an improper shut down, virus infection and more.
You can use your installation disk to do a Windows repair.
Choose to repair.option
Choose" Troubleshoot > Advanced options > Command Prompt
When in Command Prompt type the following commands in order: "bootrec /FixMbr > bootrec /FixBoot > bootrec /ScanOs > bootrec /RebuildBcd". Remember to press "Enter" after each command and wait for each operation to finish.
Reboot when finished.