not very much unfortunately
normally this starts when a new usb deviceis inserted and the full detect new hardware doesn't complete - generally because it's not given enough time.
the system sees the error - locks it - and then sits and sits and sits - xp is bad - but vista is even worse than xp
try plugging in the stick - go to device manager and delete the device - it could be in USB, disk drives, floppy disk or all three (keep device manager open when you plug/unplug)
if that doesn't work - it's very difficult to do more without redoing the system.
I still have one that won't open on my main machine