the thing is this laptop was designed before windows 7, the drivers on the Sony web site are at best designed for windows vista.
that said, and knowing well windows 7, I would say if you have the Cd, to simply boot from it, assuming you made your backup of the data you needed from it before) during the install select decide , and delete all partitions on the hard drive then install it, something may not function when all done (network cards are a common occurrence) if that happens you can download the vista drive for it from Sony and run it and see if it will run, or trying to identify each hardware piece not function in device manager and look for the hardware ID # and google search for it, it is possible manufacturer (like intel or...