External HDD stop local HDD from booting

As the title says, my windows xp just freeze (at the screen showing the word 'windows xp' and a progress bar) when trying to load from local HDD every time external HDD is connected. This problem still occurs even after I change the boot order. Everything works just fine when the external HDD is not connected. And one more thing, it happens to my Acer Aspire but not to my Fujitsu laptop.



Any idea what happens?

how do you plug this hd in?

By USB 2.0