steaminshrooms

I found what might be an answer to your problem on the microsoft help website. Since you don't have a vista CD, I'm assuming you must have their startup repair feature installed somewhere on your system. If that's the case, microsoft says to do this (sorry, the formatting's kind of off when i paste it):

If Startup Repair is a preinstalled recovery option on your computer:



1. Remove all floppy disks, CDs, and DVDs from your computer, and then restart your computer.
Click the Start button , click the arrow next to the Lock, and then click Restart. button
2. Do one of the following:
•If your computer has a single operating system installed, press and hold the F8 key as your computer restarts. You need to press F8 before the Windows logo appears. If the Windows logo appears, you will need to try again by waiting until the Windows logon prompt appears, and then shutting down and restarting your computer.
•If your computer has more than one operating system, use the arrow keys to highlight the operating system you want to repair, and then press and hold F8.
3. On the Advanced Boot Options screen, use the arrow keys to highlight Repair your computer, and then press ENTER. (If Repair your computer is not listed as an option, then your computer does not include Startup Repair as a preinstalled recovery option.)
4. Select a keyboard layout, and then click Next.
5. Select a user name and enter the password, and then click OK.
6. On the System Recovery Options menu, click Startup Repair. Startup Repair might prompt you to make choices as it tries to fix the problem and, if necessary, it might restart your computer as it makes repairs.


Once the repair console comes up, follow AndyP's instructions. (You may have to disregard step six above).
If you don't have it pre-installed, you can try to boot into safe mode with command prompt. if you don't know how:
http://www.vistax64.com/tutorials/88009-safe-mode.html

hope one of these helps. if not, the only other thing i could think of would be making a bootable disk with the utility on it, but that's way over complicated. hopefully if neither of these options helps, somebody else with more knowledge can lend you a hand.