Now, you say minimum lag, which is the largest obstacle for in-game recorders.
FRAPS is a good recorder, but also the one of the most demanding recorders out there. And with your Athlon 3700+, you might have a problem. I have a better specs than your but I even have trouble.
Gamecam is slightly faster, but much worse looking than FRAPS.
Please look at this source for more alternatives. Trial and error will get you the one that suits your needs the most.