I would suggest you to download a standalone pack of Service Pack 2 and install it in Safe Mode.
Refer the links below for more information on Service Pack.
How to obtain the latest Windows Vista service pack
Depending on whether you are running the 32-bit or the 64-bit version of WindowsVista, you may download the Pack from the links given below.
To determine whether you have the 32-bit or the 64-bit version of WindowsVista, click the Start button, right-click Computer, and then click Properties.
If you are running on a 32 bit Vista edition, you may download it from
If the Operating System is 64 bit, download the pack from