Ok, i got it today. I got:
AMD Athlon 64 2800+
512MB Elixir DDR400 SDRAM (1 stick)
400-Watts 'Win Power' PSU
Gigabyte K8NS nForce3 754-pin Motherboard
Toshiba Samsung 16x DVD-/+RW
All together, it cost me £210.
I used a 40GB ATA 7,200rpm HDD with it and installed Linux Fedora Core 3. Sadly, i was disappointed with FC3, so i'll have to wait until Windows XP is installed for me to be able to notice the power of it, as i'm a total newbie to Linux. Thanks to everyone for their help, and hopefully, it's money well-spent!