If you just want a fresh start like I did when I first bought my laptop, here is the easiest way to do it without buying more DVDs, software, etc:
1. Use a torrent program to download a copy of Windows 7 and look at your key on the bottom of the laptop for the exact version you need, ie. 64/32 bit, Home, Pro, Ultimate
2. Burn the ISO to a DVD when you get it downloaded
3. Go out on the internet before you reformat and make sure to at least grab your network device drivers so you can install and connect to the internet immediately after formatting is done. This way you can let Windows find most of the drivers it needs off the internet.
4. Install a fresh copy and then install drivers and software you need, antivirus, firefox, etc, etc.
5. ???
6. Profit
I bought a new laptop December last year that did not have a Windows 7 DVD with it. I never even started it up before I did the above steps and reformatted to a fresh copy of Windows Home 64bit Premium. Keep in mind, technically, downloading the OS DVD ISO is not kosher but it is not really stealing the software since you do own a full legal copy of the OS when you bought the laptop and all your are doing is downloading a new copy of the media since you "lost" yours. Hope this helps.
Edit: And Keypek's advice above is fine if you want to go back to factory setup but I would suggest a clean slate cause you probably don't need all the bloatware crap that comes with the machine stock.
-----signature-----
The VNboards are so much fun! Its like my own personal train wreck going 24/7
and noone is actually getting hurt which takes away the guilt of watching.