Christop is correct, your Vista copy is linked to your laptop...
BUT, while your updating :
Win 7 32 bit version should work just fine (you might need to hunt around for some drivers if you system is old...)
But if you want lots of RAM:
Do a bit of research on your laptop. Will it support 64 bit version of Win 7 ? Hey, a 32 bit OS can only support 3.25 Gb of RAM so, if you want to take full advantage of RAM I'd go with the 64 bit version if you can.