Verbatim hard drive problem

Hi there,
I recently bought a Verbatim 500GB external hard drive, and I've noticed that everytime I turn my computer off (leaving the external drive on), then turn the computer back on, it goes through the POST test ok, but when handing over to Windows XP it hangs on a blank screen where I have to turn the external drive off and restart the computer. Strangly enough, if just restarting the computer, not turning it off, its fine with the external drive being on.

So basically, when turning the computer on, I have to make sure the external drive is off. Once the computer has made it to Windows only then can I turn the external drive on.

Any help please?

Thanks


Ninko