Thanks for all the replies
Having done a bit of looking around I'm thinking of getting something along the lines of:
Mobo:
Asus A8V-E Deluxe
CPU:
AMD (Venice) Athlon 64Bit 3200+ Socket 939
Case:
Antec Sonata II 450W
Piccie drawing card thing:
Gigabyte GeForce 6600GT 128MB PCI-E
If any of you are reading this thinking 'what, he can't possibly be thinking about that pile of junk/daft combination/etc' please let me know