whats the difference?

both sticks use mT -5BC chips as far as I can tell. yet one stick is taller than the other. the taller stick wont boot windows, i keep getting BSOD or errors..
is it registered/ecc mem?

more information needed. have you got them both running at spd settings while trying to boot into windows? same voltage? Im not sure if registered memory will work on a unbuffered system. i seem to remember reading that if you dont have ecc support onboard the memory just wont use it but i might be wrong. you should post the info those stickers have on them. there would be a registered or ecc somewhere on it.

i tried running JUST the taller stick in the first dimm slot, on auto settings. the mobo should detect what ram it is and set the CPU:mem ratio accordingly and the timings. on auto it wont boot. i tried enabling ECC on the mobo and it still would get errors or reset while loading windows. there were a bunch of other options once i enabled ECC but i didn't know what any of them meant lol... the shorter stick runs great though, -5BC is great stuff, did 233fsb w/o any hassle..

No, they don't appear to be registered or ecc.

so im guessing the 2nd stick is fried since i cant get into windows with it alone?

That's my guess, RMA that bad boy.....