Hi I'm building a new rig for a friend of mine. System description: Intel q8200 Asus P5K-EPU 4 GB Ram Buffalo DDRII-800 2x2GB 2x Asus Radeon 4850 in CF 2x 250 GB Western Digital SATA II 16MB PSU: Thermaltake toughtpower 750W modular Windows XP Pro x64 System trouble: When ever there is a big data transfer, like copying a 4-5 GB file from a hard drive to another or by network, or reading / installing from DVD or virtual drive, the system restarts. For half a second there is a blue screen but it goes to fast to be read. I have tried to install windows on both the hard drives (i thought that one of them may be faulty), no success. I have ran with success memtest over and over, no error. And one more thing. When copying from a hard drive to another the speed is incredible fast, but it also freezes the system the returns to normal, freeze again..etc and 99.99 % restarts. After the restarts on random occasions windows wold not start and give an error that some files are corrupt. Restart again, windows loads well. When i manually restart sometimes windows loading screen would freeze for a minute the load normally. What i believe: I think that the motherboard / sata controller may be faulty. Should i just rma it, what other test should i do first. PS: also after 3 clean system installs and all Microsoft updates, and most recent drivers + bios updates etc, in device manager i have "high definition audio interface" or something like that (even microsoft has a windows update on that stuff), who is impossible to install although the on board sound runs.