Answer:
If you have vista then you have a somewhat new computer. That computer came with a box of discs and in those discs there should be an operating system CD, simply put it in your CD-Rom drive, boot up and press any key when it asks you two then follow the on-screen prompts, after this process (vista+fast comp. = 10min) it will reboot and show you the first couple of screens. go through-out the rest of the discs that came with the computer to reinstall drivers and applications.