Can't use any USB devfices

if i boot with anything usb connected, it wont go past the bios splash screen. if i plug a usb device in after the computer is already running it'll bluescreen after a few seconds/minute. i've already updated/reinstalled all the usb drivers, motherboard drivers, windows service packs, and automatic windows updates. WHY?

Check the boot order in your bios. If theres USB on the list, remove it, or else your computer will be trying to boot from your usb device. Usually the order is 1)Floppy 2)HDD 3)cdrw

Try resetting the CMOS. If that doesn't fix it, run system file checker. If that doesn't fix it, clean install.