When I plug both a Lexar 512mb flash drive and a PNY 512 flash drive into the usb ports of either of two Dell laptops running xp home, both drives work perfectly. The drives appear in Device Manager under Disk Dives, with the usbstor.sys driver, xp's mass storage driver. When I plug the same drives into my Asus P4P800-E Deluxe (Intel 2.8 GHz) running xp pro, I get an "Unrecognized Device" message. The drive doesn't appear under Disk Drives in Device Manager, but an "unknown device" message appears under USB Controllers. All three computers show that usbstor.sys resides in Windows\system32\drivers, but the Asus will not load it or recognize the drive. The only time I've gotten the Asus to recognize the drive is when I removed it in Device Manager and then had Add New Hardware search the XP Pro installation disk for a driver in the folder containing both the usbstor.sys and the usbstor.inf files (I386). Obviously, I can't do this every time I want to use the flash drive. This is the only USB device with any problems. All three machines are running SP2. I've seen several posting on other forums where people are having the same problem with flash drives or similar devices. When they finally get through to tech support, they're told to download usbstor.sys and usbstor.inf. But everyone has the same problem: how to get the machine to load it. Any suggestions?