Is this memory bad?

I currently own 3x 256mb pc2100 memory. Two came with the system, the third I bought from Staples (Pny). I installed the third stick of memory, the mobo beeped at me, I shut down, reinstalled the stick, and booted up. Everything was fine, til windows reboot on me. I tried again, and it rebooted, so I shut down and took the ram out.

My question, is the stick of PNY bad? Or am I just a putz that doesn't know how to install memory? Should I re-install the mem? OR just return it?

Try installing the PNY stick by itself, and try testing in all 3 slots. If it still doesn't work, most likely it's not compatible or the RAM module is faulty.

what brand of ram came with the computer?
it might be that the ram cards are not compatible, or that the pny ram isn't compatible w/your mobo. some mobos are picky with what brand of ram they take...i'm not that much of an expert, but some things that might be considered...

you can try the pny on its own in slot1 & see what happens...

i don't know about all 3 slots...i'm not sure about the newer mobos, but some that i've come across some that require that there is a ram card in slot 1 to boot up.

Some boards just don't like all ram slots to be full. My KT7A-Raid (received as RMA from Abit and it's going back soon cuz it was junk out of the box, unlike my original which was sweet, until the caps went!) gets real unstable with all 3 Dimms full. Had to run only 2 modules.

I think my board is very obsessive about how the ram is inserted. I put only the PNY in slot one, booted up, played a game for about 30 minutes, no problems. I dropped the other two sticks into slots two and three, the mobo beeped at me, I shut her down and took out the third stick. I booted once again, and it beeped at me, so I pushed the stick a littel harder (was already snapped in place). I booted up and It was fine. So I put the third stick in and we're fine! Thanks guys, I was about to take this mem back

just run memtest86 with all 3 sticks to see if their compatible with each other.