Click the Windows logo on the start menu, and type system restore in the text box, when System Restore apppears in the menu click on it and follow the prompts. This will only take you back to a number of last known good configurations, there should be a list of dates that you can roll back too.
If you want it to be factory fresh your going to need to format it, this will require the use of a windows vista setup disc.
Holding the "F" key (usually F4) during boot up and then pressing F8 once the menu has loaded, will only give you the options to start the system in SAFE MODE, SAFE MODE WIH NETWORK PROMPT, or START WINDOWS NORMALLY. And a few other prompts that wont help you, Ive checked this on my laptop.
Your going to have to Roll Back or Reinstall from a disc.
How come you never got the disc, did you get a Windows Vista upgrade disc? You can re-install using that.