You could try using vnc, you'll have to scroll about a bit to be able to see the full screen but it works.
Also if you just want your pc to play MP3's there is a free PPC program called Vinyl (
http://www.pocketwerks.com/ ) that lists songs that are on your pc so you can remote control play them through winamp and make playlists etc from the ppc.
I'm just thinking about how i'm going to control my pc from my ppc at the mo, only want it to play music at the moment untill someone brings out a nice in dash vga screen and then i'll get one of those. Got the PC ready and most of the wiring is in my car, just need a psu.