I am having HP Compaq DX2200 laptop and I am trying to upgrade the Main Memory (RAM) from 1GB to 2GB. When I bought the RAM and fitted it properly in slot, the BIOS setup was showing main memory as 2GB. But it wasn't recognised in Windows. Then I upgraded my BIOS and now it shows CMOS checksum Error - Unsupported Memory Configuration. Power Off and Remove DIMM. Later I found that the Original DIMM was 667MHz and the new one I purchased was of 800MHz. Is there any trick so that I can have RAM of 2GB. PLease help me out.