Ok,
Run a
sfc /scannow command to see if it will fix the problem. This will show you how.
How to Repair and Verify the Integrity of Vista System Files with System File Checker
Try to
Merge the .reg file again.
If this still fails, then you can do a Repair install. This will show you how. Just be sure to backup anything you do not want to lose in case something goes wrong.
How To Perform a Repair Installation For Vista
Shawn