So recently I was looking into overclocking my computer, I just copied an easy method a YouTube video showed me but then the cores got pretty hot and I didn't pass a stress test (computer turned itself off during it). So I went into the BIOS and reset everything to default and everything seemed to be running fine. A few days later and I notice it's all slowed down quite a lot and I've just identified that the problem is the RAM. Task manager shows me that my CPU usage is usually pretty low but my physical memory is usually pretty high (admittedly partly because I have lots of pointless applications, but they were all there before and it was running fine). I bought this computer with 6 GBs of RAM but the Windows Vista Welcome Centre shows only 4 GBs now for some reason. I don't understand why because I haven't even opened the computer at any point, so it's nothing physical. When I use a program call CPU-Z, it shows what's in the image attached as 'cpu z.jpg' So CPU-Z recognizes that I do have 6 GBs of RAM, so why doesn't Windows Vista? I've reset everything to defaults in the BIOS. Here are my specs if you need them: CPU: Intel® Core i7 920 CPU Cooler: Coolermaster V8 LGA1366 Motherboard: Asus P6T SE (Intel X58 chipset, IncludedCrossfire) Memory: 6.0GB Corsair DDR3 1333mhz XMS3 CL9 Hard Drives: 500GB S-ATAII 3.0Gb/s Optical Drive: 5x Blu-Ray ROM S-ATA DVD±RW Second optical drive: 20x DVD±RW DL S-ATA Lightscribe Graphics card: NVIDIA GeForce GTS 250 1GB Sound card: Asus Xonar D1 Operating System: Microsoft® Windows Vista Home Premium SP1 64-bit Accessories: PCI Digital TV Tuner Card PSU: 700W EZCool Tornado And yes, I have run Windows Update and stuff - remember, it used to show 6 GB and I haven't uninstalled anything, so it should still be able to. Would seriously appreciate any help on this one. I have uploaded pics of the BIOS.