Ive recently bought 512ddr ram for my compaq presario 900 laptop to give my system a boost. My laptop allready has 256 ddr ram, both ram will work on it own but when i try use them both together the laptop wont boot in normal mode but will in safe mode. I was wondering if this could have something to do with my bios or is the ram not compatible with each other, the ram is exactly the same just is different makes