Dell E521 Doesn't Boot Past Dell Bios Screen

Hi All,

I have recently bought a usb external hardrive for my PC, it works fine, however, whenever i restart my machine, the status bar on the Dell splash screen (on startup) doesnt move it gets to half way, then stops.....But when i disconnect the external hardrive from the USB port, it loads as normal and then goes to the normal XP windows splash screen.

Does anybody know whats going on or has anybody faced the same problem?

Thanks in advance.