My vista 32 bit keeps failing to install windows service pack 2 is there an alternative?

it goes up to step 3 at 100% then starts up the computer and gives me a message saying some error code, and that service pack 2 installation failed, can someone please help it would be very helpful I JUST WANT TO KNOW IF THERE IS AN ALTERNATIVE OR A FIX FOR THIS , BECAUSE IM TRYING TO INSTALL SONY VEGAS PRO 10 AND I NEED SERVICE PACK 2 TO INSTALL IT THANX xD