Will this work?

AMD Athlon 64-bit 3200+
512 MB DDR
Nvidea Geforce FX 5500

I guess it works..

It should run, not at the best settings but should be playable / still look good.
I'm not that far away from you in specs:

Amd Athlon 64 3400+
1gb DDR
Nvidia Geforce FX 5700 Ultra

Download the GW client and give it a try, even the login page is rendered in the same game engine (even if you don't have an account).

I ran 512mb ddr when I first got Guild Wars and maps loaded a little slow, so I bumped up to 768 and its much much better.