|What is the make/model of your machine? |
It sounds like the recovery partition on the hard drive may have become corrupted or has gotten deleted. In this case you will need to insert the recovery CD that came with your machine. If you do not have the original CD/DVD recovery disks, you can normally purchase them from your computer manufacturer for a nominal fee.
Let me know if you still need more help.
IT Desktop & Network Consultant - MOS Master Certified, MCP, MCSA, MCITP - Windows 7, CCNA Certificate Pending, A+, Network +