XP PC won’t boot with Freecom USB drive

I have an HP Pavilion PC which works fine until I
leave my Freecom 80 gig hard drive plugged in whereby the PC just hangs before even starting up windows. I’ve checked the dev manager and I do have Universal serial Bus Controllers (the PC is only a year old) If I unplug the USB drive the PC will wait approx. 30secs then carry on booting. can anyone help ??