My mobo will accept up to PC100 and i have 128 mb of pc100 on it now.Will it accept a stick of pc 133 instead of pc 100.Will it reject it or accept it, and will i have repercussions from it. What would it do etc..

More than likely your motherboard will accept it, but it will only run at PC100 speed. And I doubt you will have any problems, just you will not be running the ram at it maximum capacity. If you could give us some more info, like what kind of mobo, ram, etc. you have it would be good.

Super is correct. The ram will just be downclocked to 100mhz..It should run fine.

Like what Cheetah said. If your CPU FSB is at 100, then you'll have no probs.

It won't do anything bad. It will (like the others said) default itself at whatever speed the FSB is running, if its 100 then it will run at 100, if 66 it will run at 66. PC-133 is great to have in your case because when you deside to upgrade further, and you don't want to use DDR ram, you already have a stick of the 133. If you get good quality ram you may even be able to push it further. For instance, I had some Micron PC-133 rated at 148, so I could change the memroy speed "UP" to take advantage of the extra bandwidth. It was small but every bit helps...!!

If it's an old motherboard, just make sure you get a single sided ram module. Old motherboards can't use double sided ones & you'll end up only having half of the ram module's capacity detected.

Actually, it may not even be able to detect the RAM module. I have an ASUS P2B mobo and I tried to insert a 128MB RAM module in it. It didn't even detect it. , in fact, the system didn't even POST.

Did some digging and found out that older mobos only support 64Mbit (not bytes) modules. Can't remember exactly how that is derived though...

I have a soyo sy-5ema v 1.1 mobo and two sticks of 64 mb pc 100 sdram