You can use the Vista DVD and boot from that to get to the Restore point option.
Recovering the Vista Bootloader from the DVD - NeoSmart Technologies Wiki
If you look at the stuff here the first screen shot shows you what you have to do.
Click the Repair your computer link. The 2nd screen shot shows you what window will come up from that. There you will see the System Restore option listed.
Select that and it will search for Restore points that you can use. Just use any of them listed before this problem occured.
Recovering the Vista Bootloader from the DVD - NeoSmart Technologies Wiki
If you look at the stuff here the first screen shot shows you what you have to do.
Click the Repair your computer link. The 2nd screen shot shows you what window will come up from that. There you will see the System Restore option listed.
Select that and it will search for Restore points that you can use. Just use any of them listed before this problem occured.