Install windows on external disk

I am trying to install windows on external disk and cant do it. When i have to choose on which drive to install i choose external one but it calls some error. Are there any special windows for this purpose? I am using usb disk, do i need firewire cable or something else?
Answer #1
as long as your bios supports and has enabled boot from usb drive there is no reason I am aware of to prevent doing what you want details of the error would be helpful
Answer #2
Windows XP refuse to install on external drives…But there is a work around…Have a look here:
Installing Windows XP from USB
http://www.vandomburg.net/installing-windows-xp-from-usb/
Answer #3
This should work. I installed Ubuntu and Windows XP to my external HDD the the other day.
Answer #4
Thanks for your time but this is tutorial on how to install windows xp from usb to internal hard drive, i am trying to install it on external hard drive from windows xp cd… any ideas?