check this link, it might be helpful

Re-partition a hard drive is advance subject, you might have the mind set that you need to do recovery if changing of the partition fail.
Didn't know what you have changed in the partition. Try checking the volume under diskpart if you can access to the command prompt.
If the partition is there and it won't boot, you can try repair the system from a Vista boot disk.
(bootrec /fixmbr,bootrec /fixboot)

http://www.bleepingcomputer.com/tutorials/tutorial133.html

all the best