All my USB ports doesn't works. It happened just recently, i don't know when it happened. I tried to reinstall windows XP but still doesn't work. i wondered what is happening. The usb ports are connected to motherboard. Is it some wires are loosen or what? i don't know what to do, please help!!!Thanks!

go to safe mode by tapping the F8 key while booting, choose safe mode, enter with the admin account. once there right click my computer,,properties,,advanced..hardware,,device manager,,click the plus sign at usb and remove the entries, reboot and let windows reinstall them. UNplug all your usb devices before doing this then replug after it is done reinstalling the ports.

How old is this system? Upgrade or clean install to XP? How did you "reinstall XP", and I ask that becasue there realy is no such thing unless you reformatted and installed fresh XP. Do you mean you did the "repair" instead of reinstalled?

thanks for help, it is related to a bios issue.