Originally Posted by tewald
I have read that I should make changes to GRUB, but I can't even access the Linux drive to do so.
Isn't the install CD for Ubuntu a liveCD? Meaning you can boot and run that as a Linux system itself.
While in that Linux system, you can see which partition you have Linux installed in (such as /dev/sdc1 if it is the first partition of the third drive and if naming is following the usual rules) and you can mount that partition and modify files in it including the menu.lst file that tells the stage 2 of grub what to do (once you've managed to get stage 2 of grub actually started on that drive).
Also in that liveCD mode, you can run the command line version of the grub installer. I don't know what the GUI installer for Grub in Ubuntu lets you do. The command line version lets you do what you want. In this case, you want to reinstall GRUB with stage 1 going into the mbr of your third hard drive (meaning it goes in /dev/sdc if drives are named the way I expect from your post).
The last complication is figuring out which number the third drive should have inside menu.lst. If the drives were numbered normally, then the original installer probably numbered it '2', which may be correct. But when the BIOS changes boot sequence for the SATA drives it might also change the numbering of the drives in menu.lst, so your third drive would still be sdc in Linux but when grub gets control from the BIOS it might be '0'.
All of the above assume you want to use the BIOS to control the dual boot, so you want Windows stage 1 loader to stay in the MBR of physical drive 0 and Grub's stage 1 to go in the MBR of physical drive 2.
The more common method is to put Grub's stage 1 in the MBR of drive 0, destroying Windows stage 1, then put something in menu.lst to allow Grub to transfer control to Windows during boot.
Another way is to use DD to make a copy of Grub stage 1 (after figuring out where it was installed or reinstalling it to the partition boot sdector). Copy that with dd to a Linux file, then through whatever media you can access copy that to a file in C:\ of the windows system. Then edit the Windows hidden file boot.ini to tell it to boot Linux through that file.