Download 64bit drivers first, back up all you settings and data with w7 easy transfer, get all your software (including downloading utility applications from the manufacturer) and make sure you have all your product keys (freeware like SIW can help), then install from 64bit disc.
NOTE: If your computer did not come with discs then you likely do not have 64bit OS at all so you will need to download the ISO (make sure you get 64 home prem if you have 32 home prem, pro for pro, or ult for ult) and burn it as Kalario mentioned.