what should i buy?

Well for graphics get a Geforce 4 Ti 4200 based card. Best choice right now IMHO. Best next choice out of Nvidia chipsets (but a serious step down): Geforce 3 Ti 200.
Most people in here will probably vote for an Athlon/VIA CPU/mobo combination because of it's best bang for the buck in N64 emulation but I personally would never buy anything VIA related.
I much prefer having an intel chipset even if it means I pay a little more and have a few fps less in some applications. I use my computer for vastly different purposes so it's not optimized for a specific application but rather for general performance / quality / stability.

If I would buy a new comp now I would slightly modify my current specs to: Asus P4T533, Pentium 4 2.0A.
If you are seriously interested in good N64 emulation save a couple of bucks for an Adaptoid and a real N64 controller. You won't regret it!

as long as ur past the 1GHz cpu / 256mb ram / 64mb gfx card standard, your comp should be more than good enough for n64 emulation. Of course, you should get as good as possible to prepare for the future.

to reiterate Corak, get the adaptoid & n64 pad dammit!

Putting this in TechTalk.

u don't need a 64mb gfx card for n64 emulation... really (roll-eyes)... 8mb should be ample... 16 if your feelin generous

ya, but ke would probably want a good res, FSAA, etc

anyway, i said "More than enough", Smiff...

32mb at least..