Take a look at my signature "Just Booting Tips". All the answers are there.

You can do it with a Live CD or a bootable Grub floppy. These two tools were all I had to boot the 100+ systems which are also described in another link of my signature.

hi i have a similar problem, i run suse 9.2 on a usb hard drive, and windows xp on my laptop hard drive, toshiba a40 satelite pro, I installed suse 9.2 fine on the usb drive, but i have to use the linux disc one to boot, as when the laptop boots up (not from cd) then i get the messege 'Grub hard disk error', i have tried reinstalling the boot loader, changing it to lilo etc etc but nothing!
if you do find a solution let me know eh? cheers

btw, i only use the Linux, i have all my programs running on it that i used to run under windows, most have linux counterparts, plus have you noticed how much faster linux is? brilliant