I've recently installed a WinXP/LinuxMint Dualboot on a new PC for a friend of mine.
The Installer always quit at 94% with the message "grub-install failed [...]" as posted by some other people. But no solution I found on the net worked. When I tried to install grub from the console with "grub-install" there was an error message stating that "stage1 not read correctly". So I redownloaded the image and burned it with a different program but the error remained.
I found the problem when I finally ran fdisk. The partition I chose for Mint was shown as FAT16. After changing it to Linux everything went as smooth as it should. My mistake must have been to create the partition for Linux in Windows.
Perhaps future Versions of the installer's partition editor should check for the correct flag in the partition table. Or perhaps I'm wrong and there was a different problem. If I find some time, I'll wipe my current gentoo installation and try to verify this by installing Mint on my laptop.
I hope this was helpful for someone.




