I have 4 (1gb) sticks of ram (ddr2-675). My system refused to load to desktop recently ( Ive had the sticks since Febrary). WHen I took all of them out and put my spare ddr2-533 sticks it loaded to my desktop. Also I then took out the ddr2-533 and put one ddr2-675 stick in and it loaded but when I played a game I got the blue screen of death. I shut my system off and took out that stick and put another in. For a few hours I was on the computer again playing a game and I never got the BSOD. Does this mean the other stick was bad? I have the 3rd in now and everything seems ok.
I'd suggest you send the bad stick back for a good one or if it's not under warranty throw it out. The only reason I would run something that I knew was bad would be a hard drive I had to get data off of. Why take a chance of really screwing something up?