Originally Posted by Praetor

The upgrade version works only if you have either an installation or the older discs (not sure if older "upgrade" discs work).

The non-upgrade versions you can use without the restriction of having an older version of windows.

Between home and and pro, decision is yours depending on your needs:
http://www.microsoft.com/windowsxp/e...n/compare.mspx
http://www.microsoft.com/windowsxp/p...choosing2.mspx