Hi folks, My first post here, so I'm hoping somebody can help! I have a Compaq Presario 2500, model 2548AI, made 2002. This laptop was supplied with a Hynix 256MB PC2700 DDR333 SODIMM, Compaq part, which goes OK though the manual (and the HP site) says it takes a 266MHz PC2100. I have tried to upgrade with 2 x Legend 512MB PC2700 DDR333 SODIMMs, but the computer will not boot. The manual says that it should take up to 1GB of RAM in two 512MB modules. Both the original 256 card and the new 512 cards use the same brand of chips, and seem to have the same specs: DDR333, unbuffered, 2.5v, CAS latency 2/2.5, and have eight Hynix chips per card. I have tried the 512 cards in both slots - no boot! But the laptop does boot with the 256 card in slot one and a 512 in slot 2. However BIOS only reports the 256 RAM, and there is no option for selecting more. It has been suggested to me that HP somehow fix their their laptops so they only take HP supplied parts, which of course cost up to three times more than similar third party parts. Is this correct? My thoughts are that any comapatible RAM cards should work?