So I've got 256MB RAM@266mhz, on an viaKT400 motherboard(suports fsb 400mhz)...
Now I'm going to buy myself another 256MB RAM, and I noticed that those @400mhz are for some reason cheaper than those @266mhz...
My question is if I'll have one module @266mhz and one @400mhz, will my PC work correctly, what will happenn, or should just buy another module @266mhz even though it's more expensive?

I'm not sure, but I think that if you buy one, make sure it supports 266 mhz FSB. Compatibility problems _might_ occur, still.

Are you talking about DDR ram or not?

Both are DDRAM but one is @266mhz and the other is @400mhz...

Mixing different RAMs is almost always a bad idea :not_ok:

When you say @266 you mean it is a 133Mhz memory? Oh, I don't know how good it would be to combine the two. Is the 266 even of the same voltage, I guess it is since it is also DDR, but, hmm, You can always try....But, it would be better to buy another 400 one.

The thing if I buy let's say one DDR Module of 512@400mhz (the 256 I have now is @266mhz) I would have too raise the FSB of the whole motherboard to 400mhz, so that would mean overclocking the processor at least one guy explained me this way...
He told me that 400mhz memory would work on 266mhz(if I keep the old module that I have and add a new one), but I'm still not sure though...

So, selling that 256 @266 is out of the question?

hmm i thought the ram would automaticly run on the slowest speed of the two.

doesn't the pc shop know this btw ?

No PC shop I'm buying used RAM...