Ok, here's the deal, I have 4 gigs RAM, Windows only reads 3.25 of it, I've been told this is normal. I have an nVidia GeForce 8800 GT Superclocked with 512 megs GDDR3 RAM and the latest drivers. I have a 500 gig SATA 3.0GB/s HDD, and a 3.0 GHz Dual Core AMD Athlon 64 X2 CPU. What's really bothering me is, I just went back to XP from a long time with Vista, which had it's quirks but I kinda liked it (atleast it read all 4 gigs of RAM). I'm trying to use my computer to it's full potential (you can imagine with those specs, it SHOULD be fast), but it's just not up to par. I don't know if it's just me, I don't think it is because I'm not the only one noticing it, but it seems to take a lot longer to do anything. Before (Pre Vista XP installs and even with Vista), folders displayed instantly, now it takes up to a second to display a folder and it's contents. This doesn't seem like much, but I move around a lot and it adds up to a lot of waiting. I used to be able to play Halo 2 at 120 FPS with max settings in 1920x1200 resolution, now I can't play Halo 1 at even 30 FPS, and I need to use FRAPS to record stuff sometimes at 29.97 fps, it drops to 25 fps while recording and skips around. It shouldn't be the disk access, because I've played the game enough that the relevant information should be resident in memory. I just went through the process of isolating my computer and unistalling programs, and I'm defraggng too, but it's not really helping. I know I don't have a virus because I have a clean install of XP (just a few days ago) and AVG free version 8. What else could be causing such a dramatic loss of performance. It's really frustrating to have put almost $3000 into my computer and to have it crapping out this badly. Does anyone have any suggestions, maybe some tools that I can run to diagnose any performance hits? Thank you. Oh, P.S. I make sure to kill any TSR programs and processes running that are not directly needed for what I'm doing BEFORE I play Halo, the only thing I keep running is FRAPS, which uses approx. 22 megs of RAM, and 0% CPU (at the moment). Please help!