upgrade win xp home sp2 to pro sp1.....

I'm new here so sorry if i put in wrong place...

I have windows xp home service pack 2 installed on both my desktop and my laptop. they were installed with service pack 2, not upgraded from service pack 1. i need to run xp professional on my computer to run .net stuff for visual basic studio for school. i get a free upgrade for xp pro but it is service pack 1. when i try to upgrade, it says i cant because i have a newer version of windows installed on my computer, and wont go any further than that. i cannot "roll back" to service pack 1 because it was installed from a service pack 2 cd, when i got both of my computers now. does anyone know what i can do to get the cd to install besides formatting my hard drive and installing the win pro service pack 1? i have a 120 gig hardrive and like 60 gigs is used from programs and files for school, work, games, and other junk.

any suggestions will be rockin... you can email me direct at
[email protected] or post here... whatever works best...

thanks alot to those that can help