- you really are an old grump, aren't you?
Not really, only when it comes to XP clinger-ons.
Answer - by deleting the Windows folder?
Aah... well, you didn't make that bit at all clear. So basically you're turning it into an external hard drive with your old files on it. Which is fine... as long as you don't connect it to an XP machine !
You will of course break your software at the same time as Windows, but you knew that I guess.
But really, if I were you, I'd look at a clean migration to 7 or 8. And then only move accross files you really need, and install software from scratch.