Guys this is the spec of my PC: Motherboard: MSI MS-7093 RAM: Memory Installed = 512 MB (2 x 256) Maximum allowed = 4 GB* (4 x 1GB) requires the replacement of the installed 256 MB DIMMs *Actual available memory may be less* Speed supported = PC3200 MB/sec Type = 184 pin, DDR SDRAM DIMM slots = Four (4) Open DIMM slots = Two ok as u see, i have 4 channels. 2 occupied by 2x256MB (PC3200) HYNIX I just bought an extra SAMSUNG 512MB (PC3200) [so shuld have 1 gb ram] installed..it only detected a max of 768MB. i tried ALL sorts of combinations 1st 2 channels are blue 2nd 2 channels are black. is it true they should be ONLY in pairs? therefore, i shuld get rid of my 2x256MB and get another 1x512MB?