You should be able to `Repair` Vista click here and recover your files/data with (hopefully) little or no loss. You will need a Vista CD and the Windows Key which should be on the PC.
By turning off the PC whilst it was still writing you may have damaged the data which forms the OS, you may also have damaged the HDD but this is less likely.
In the event you are unable to repair Vista, the only other suggestion I can make is for you to remove the HDD from the PC put it in a caddy (external HDD enclosure) and plug that into another PC as an external drive. This should allow access to the drive contents.