Unique(I believe) installation problem

[Hoerne]

I decided to install Ubuntu on my external hard drive, while still having windows as the main OS on my internal hard drive. I installed it on my hard drive, and now whenever I turn on my computer it gives me a GRUB error(21 I believe without the external hard drive turned on, 15 I believe when I don't have the Ubuntu CD in the cd drive, and 2 when I have the ubuntu cd in the drive and try to choose boot from first hard drive).
My question is: How can I fix GRUB so that I can access both windows and Ubuntu?

[AlphaLexman]

I tried this once about 9 months ago, never got it to work tho. Gave up and bought and additional internal hd for linux & grub.

I think you would have to set your bios to boot to usb (if that's how your external hd is attached) install grub to it and manually add the windows info to the menu.lst.

I know this is vague info but something I gave some thought to but never tried.