An upgrade is only if you have a previous version of windows on your computer. You need to buy a "full version". Just look for the one that's more expensive... that's it. Also... are you using 64 bit hardware? Such as an Athlon 64 or a Intel Core 2 series? If not don't bother wasting your money an an x86 (64-bit) of windows. Of course, if you want to install more than 3 gigs of ram you will need the 64-bit version.

ok thank you, im going for intel quad core i think and 4gb of RAM and i was told to used 64 bit