Having problems with usb mass storage

ok I got a new digital camara and installed it in to my laptop which has windows xp pro. but I can not use it it say found new hardware when i try to get it it can't find it. This also happens with my umm external hard drive thing. I have deleated the usb ports and restarted my computer and it the device manger under there is a yellow ! mark on it or it does not it doesn't say new hardware or even try to find it