Your install disk may not be suitable as it has to match the installed OS which should be SP2.
I assume you have SP2 installed ?
I know I can use a Win 7 SP1 Pro disk to perform an offboot sfc /scannow on my Win 7 SP1 Home Premium so I think a higher version of Vista should be able to do the same.
If that Ultimate version isn't accepted then scroll down to the bottom of this article which is for the 32 bit Home Premium SP2 version.
http://webforpc.com/software/operating-systems/windows-vista-iso-download-bootable-32-bit-64-bit/The reason for doing an offboot sfc /scannow from an install disk is because the one done from within Windows is unable to repair due to corruption or missing files from within the store.
Booting up with an install disk and doing it will check and repair files from an incorrupt source.
If the offboot sfc /scannow reports that it cannot run, then you will have to do a repair install.
If you only have SP1 installed then you can use your own install disk, else you will need to use an install disk that includes SP2.
I think that Ultimate will have SP2 installed, but it depends on the date of the article and whether the ISO download was updated.
However, the link I've posted for the Home Premium download will suffice for a SP2 version.
This is the tutorial for performing a repair install in Vista -
http://www.vistax64.com/tutorials/88236-repair-install-vista.htmlBefore performing a repair install, while Windows may download some drivers, it's advised to back up your own drivers folders onto something like an USB flash drive and then drop them back in after the repair install if necessary.
They can be found at C:\Windows\System32