HELP: Reformatting Laptop w/out Discs

[Miseryschyld]

I purchased a laptop via Rent-A-Center over a period of 3 years. It did not come with any discs. For the past month or so, it has been running VERY slowly and it's driving me INSANE, so I was wanting to know how to go about reformatting it. I searched around online and the only thing I can find is to reboot it, then hold down F10. After that, all I can do is hope that it turns back on and runs the same as it did the first day I brought it home.

In my searches, some things were mentioned about needing to reinstall drivers or something, and Vista itself? I know basically nothing about computers. I've gone through and archived all the things I want to save before I wipe my computer, then saved those files online until I can go back and download them.

My computer is a Sony Vaio. The numbers on the monitor read: VGN-N302E if that helps any. Basically, I don't want to attempt this, then basically be left without a computer. Whatever help you can give me would be awesome, but please, dumb it down for me?