If you really want help, you should give me some additional informations:Please let us know the chipset and the Southbridge of your system. Alternatively you can post the vendor and the name of the computer or mainboard. Are you running your SATA hdd('s) in AHCI or in RAID Mode? Which Windows XP x64 Pro version (without SP = SP0, with integrated SP1 or SP2?) was on your USB drive, when you tried to get the OS installed? Did you slipstream any drivers into the XP x64 image? If yes, which ones? Most important are the vendor and the version of the integrated drivers. Where did you get the Windows XP Professional x64 version from? Did you really use an original (=untouched) OS as source? Which drivers have been loaded? If you are running your SATA hdd('s) in AHCI or RAID mode, they will not be detected by the Windows XP x64 Setup, unless you have loaded (F6) or integrated the suitable AHCI or RAID textmode driver.If you really didn't load or integrate any textmode driver, then you obviously used no original (=untouched) OS as source. You can easily verify it by having a look into the AMD64 directory of your XP x64 source. If you will see a file named WINNT.SIF, the OS has already been customized by you or someone else. •Intel® X58 / ICH10R . its an asus p6t6 ws revolution motherboard. •running in RAID mode . must be RAID, otherwise RAIDed HDDs don't work in AHCI •xp pro x64 with SP2 integrated •not in usb drive, but SATA DVD drive connected via usb (acting as an external, otherwise i cannot boot with cd or dvd... it says cd rom boot priority...35, etc etc etc) •yeh, i slipstreamed ALL Sata AHCI and RAID drivers for Intel, just to be sure. my main one is ICH10R raid, and thats what i care about. i even did a floppy disk, with f6 and it said windows has already loaded them, so the drivers are loaded properely •as i said, there is no need for f6, i have intergrated them. •i think the cd has been customised, as it had sp2 on it, and i added the drivers. i added textmode drivers, and pnp aswell (after many cd's, i decided to add the whole lot to guarantee it) and the size grew by like 1 mb