Hey Guys, I am curious as to how the maximum amount of memory is detected/utilized by Windows in general. I am currently referring to a 3 year old desktop with Windows XP Home 32-bit. I have 3 GB of DDR2 PC2-5300, 667 Mhz and also an ATI Radeon HD 4890 pci x16 which has 1 GB of DDR5 dedicated memory on it. As I understand it, Windows XP 32-bit can only recognize either 3.5 or 4 GB of ram maximum. Does the ATI graphics card I have count toward that maximum, making windows see my total ram as 4 GB now. The main reason why I want to know leads to the second part of my question. I am looking to upgrade my system ram to DDR2 PC2-6400, 800 Mhz. I don't know if I should just ad 2 GB of the DDR2 PC2-6400 in place of all of the older DDR2 PC2-5300 ram or if I should ad more than 2 GB of DDR2 PC2-6400, would there be any performance issues as far as windows not recognizing part of it, if I had 4 GB of DDR2 PC2-6400, 1 GB per each of the 4 memory slots which is the max the motherboard can take on that note. Thanks to anyone who reads and/or reply's to this rather long question!