Can go from a 32 bit op to a 64 bit. Can do a clean install clean means wipe hard drive clean but to get activated need to use information, posted web site earlier. Will need to do a registry change and then will activate ok. I would try this first stick in 64 bit windows 7 and let it get info it needs and then format the hard drive before install 64 bit. This will a clean install for 64 bit. If need to can wipe hard drive clean and then install 64 windows 7, will work fine. If go this route look at info posted earlier ==== Paul Thurrott's super site for windows clean link posted earlier or click on search info link What ever way you choose to go can upgrade from 32 bit to 64 bit and will be able to get activated one way or another using info posted earlier. The way Microsoft wants you to do it say have xp 32 bit and want to go to windows 7 64 bit put 64 bit disk into machine and let windows get info from earlier install and then should get a chance to format hard drive and then install 64 bit on a clean hard drive as a CLEAN install or upgrade. If you read info from Paul Thurrotts web site the information will become clear to you. But as I said earlier will be able to go from 32 bit to 64 bit and get activated one way or another. When Microsoft learns they cannot treat there customers as criminals then every thing will be much better. Hope they learn soon. So if you have a problem with hard drive in future and need to wipe hard drive clean will need to install old operating system to reinstall windows 7 the way microsoft wants you to do it. But you still have other options to install if read info from link posted earlier.