Bubba_Jr, welcome to the forum!
I like to move things around too, on a spare notebook. If you plan on this, then I highly suggest that you buy a full retail (no OEM, no upgrade) version of Windows 7.
Speaking of 7, I also used XP for years, still do sometimes, but in Nov 2009 when I bought this desktop, for the most part, I've kicked XP to the curb. Win 7 is more reliable, requires fewer resources to run (any computer built to run Vista can breeze through 7), and is a better overall OS.
I think that you'll like it, and provided you buy a full retail (avoid eBay like a plague for this) at a reputable dealer (such as Newegg or the Microsoft Store), you can move it around all you want.
Best of Luck,
Cat