memory for my laptop

[R3N3G4D3]

I'm trying to expand my Dell Latitude C640's 256MB PC2100 laptop memory, but looking at the prices online I found PC2700 to be cheaper than PC2100 (and I'm not exaggerating either, 512MB stick of PC2100 is $60 while I already found a 512MB stick of PC2700 for $40). I know that motherboards can use mixed speeds memory modules as long as both of them run at the speed of the slower module if the motherboard supports both speeds. However, in this laptop only PC2100 is supported. So my question is, if I put the PC2700 memory into it, will it still run but at PC2100 speed (since they're both DDR1 type), or will it not recognize the PC2700 module? Also, while we're on the topic, does this also apply to PC3200 modules (will they be able to run on my laptop with PC2100 speed)?

[infinitevalence]

as long as you get DDR SODIMM's it makes no difference if its 2100, 2700 or 3200. The later two are backwards compatable with 2100.