Hi Yee,
for a single core AMD 64 3000+, any decent name brand DDR2 800 will be fine--not a huge difference between 533 and 667 speeds, but, memory is cheap now, and the difference to get the faster DDR2 800 is negligible.
Any of these will work great, be stable:
http://www.newegg.com/Product/...0%2c523%3a8477&bop=And
Kingston has always worked well for me, but, I do not overclock.
Patriot, Crucial, Corsair, Mushkin, Wintec: all very good, lifetime warranty.
HTH
NXIL