This is a relatively common, and usually serious error. My dad had this, and sent his machine 5,000 miles (from Texas to Sweden) for me to fix 2 months ago (lightning strike while machine was on ruined the hard drive).
These are the basic things that typically cause it, though there are more:
1. Corrupted Windows registry (common)
2. Bad sectors on the hard drive (fairly common)
3. Power surge or outage (fairly common)
4. Bad or partially connected data cables (relatively common)
5. Upgrading your computer or BIOS (and doing something incorrect)
6. Transferring (moving) a boot drive from one computer to another (will cause it if you do this)
7. A boot sector virus (very uncommon)
- Have you recently entered your BIOS setup? If so, what did you do exactly.
- Describe the broken key incident in much more detail...
- Describe, in detail, the boot process that appears (including number of beeps, if any) before the stop error (it is a stop error, right?).
- Updated any drivers lately (or have Auto XP updates on)?
- Have you moved your PC physically?
In short, you have a problem which will likely require you to reinstall your operating system... if you are lucky. Hope your data is backed up.
Google will help, but before you actually do anything, you might want to post first. Worst case (not determined yet though), you will need to replace your hard drive and connecting cables.