That's not a dumb question at all, it's a perfectly reasonable one. It becomes dumb only if you have to ask it twice because you forgot the answer... :smile:
The only functional difference I've ever noted between XP Home and Pro versions is that the latter can be part of a Windows network domain, the former can't. Therefore any software that depends on features of Microsoft's distributed file system won't work with XP Home. It's not easy, for instance, to share storage on an XP Home machine on a home network with adequate security and access controls... or at least what *I* would consider to be adequate security and access controls, but I'm a little paranoid about computer security.
For other things though, like the common office productivity applications like word processing and spreadsheets, utilities, games, security suites, and whatnot, my experience is that XP Home and XP Pro behave exactly the same way.
And finally, it's actually fairly straightforward to have multiple operating systems on a single machine. Mine has both XP Home and Linux on it. I've never tried XP Home and Pro on one machine, but there's no reason I know of that it couldn't be done.