Assuming you have the license key (printed on the bottom of the laptop), you can download the official Win 7 ISO and clean install.
http://www.w7forums.com/threads/official-windows-7-sp1-iso-image-downloads.12325/
If the original install is 3 years old, you're bringing along 3 years worth of old junk in the registry. Yes, most applications uninstall clean. But many do not. Why drag along that old junk?