Add a 512 stick to TWO 1 gig sticks ok?

Hello everybody! I've got a quick question about a ram upgrade. I have 2 sticks of 1gb Corsair 3200 400mhz RAM installed. I also have a previous stick of ram that I used which is a 512 mb 3200 400mhz stick (NOT Corsair). Could I add that 512 stick to my current 2gb setup? More importantly, should I add that 512 to my setup?

I've read before about mixed memory being a bad thing but I was never sure if that referred to the speed or dimm size or to the overall ram/stick size as well. Thanks for your help guys! 8)

well it depends on your motherboard, you can just try and see if it doesnt boot then it didnt work , some boards are picky and they dont let u run diff brands, then some arnt... 2 gigs to 2.5 gigs wotn show perforamnce increases and if your 2 gb are running in dual channel it may slow down performance (dont quote me but thats my guess ) so just run a benchmark or 2 without the extra 512, turn off ur comp pop in the 512 and if it boots try benchmarking again, if its higher than the first then keep it, if not ditch the 512 stick and give it to me ... good luck!