PROTIP: find out how to split your HD into two partitions, Then put Win7 on a different partition so you can boot up both.
Only a few versions of windows7 can open up windowsXP Mode with it coming free.
Ultimate is one of them.
They put XP mode in there JUST IN CASE something doesnt work with Windows7.
Its going to happen. Some, SOME, (like 1/50) programs wont work with windows7, I cant list any on the top of my head, but I know some dont.
Nothing major though.
Also, in case you dont know, most Windows7's are 64 bit.
Assuming your on a 32 bit XP, then 32bit programs usually dont work with 64 bit programs.
Again, if you have no idea what im saying, google it.