Hehe. This one was a royal pain to get working but it just goes to show what you can do when you put your mind to it!
I was thinking of games that my gf could play on my PC, and guessed what popped into my head. One of my favourite games from my 386/Win95 days. Only problem, it won't run on Windows XP. at all. So, with a little hacking, and a couple of downloads, here's the answer:

Bullfrog's Theme Park for DOS, running on Windows XP!

I don't think anyone's successfully done this before - or at least I couldn't find it by googling.

Here's how I did it.

Download this program:
DOSBox, a x86 emulator with DOS

insert theme park cd
in dosbox, type the following commands in order:

mount c c:\dosprog
mount d d:d:
setup

that should launch the theme park setup alright
then set the sound and music to soundblaster 16, install dir to c:\theme.cd and then choose 'save and install', then exit.
then type the following commands:

c:
cd theme.cd
theme

that should work.

I also used the excellent D-fend v2 to create a profile for this game, allowing me to launch it transparently from a desktop shortcut.

I just hope my gf likes the game now!

EDIT: actually, just discovered dosbox themselves list theme park as a supported app, so I guess at least a few people have tried this before! Still, I'm pleased I got it working, let's see what the gf thinks! Here's the link: Bullfrog Theme Park on Windows XP, via dosbox