what has happened is the boot partition is corrupted - you can read more here:
Troubleshooting Stop 0x24 or NTFS_FILE_SYSTEM Error Messages
you have 2 options:
if you need to recover data from the disk you have to install the drive as a slave in another computer and fix it as Tim did above.
If you don't need to recover your data you can boot from the vista dvd and delete the partition completely, then recreate and re-install. if you don't have your vista product key handy you need to use the first method.