AMD XP 2500+: $85
FIC AU13 motherboard: $80
Geil Golden Dragon DDR (256 megs): $50
TI 4200: $90
SoundBlaster Audigy: $60
Sony CD Burner: $40
Monitor: $100
Total: $505
Just a comparison (in USD). The specs I posted above are either equal or superior to what you would be getting (the Athlon XP 2500+ is overclockable to equivilant of a 3 ghz P4 if you do it right). P4 processors are expensive.

For another $50 you'd get some more kick butt RAM (I have a friend with it, it's insane stuff). You can save money by getting a slower processor ($45 for an Athlon XP 2000+). I just need to say, for what you're paying for, you really aren't getting a lot. I spent $500 on my main machine and got some far superior parts for the same price. If you really want to do this thing the easy way, order all of the parts yourself from Newegg.com and build it (they ship down under, I believe).
If I had a choice between a system using DDR or SD RAM, I'd pick the DDR machine, even if it had less RAM.
I was going to post up cost per item you wanted if you got it off newegg, but they don't even have P4 2.0ghz processors anymore. @_@; Newegg has an insane RMA policy. If you fry something, they'll replace it.

Even if you did it on purpose. And if it would have voided your warrenty if you had purchased it elsewhere. They will let you RMA anything as long as it has no physical damage (unless your motherboard was defective and burnt to a crisp or something).
Niku san wa tomodachi desu.
~Chi san