Stewie (sorry, I'm a Family Guy fan
If your PC is set (in the BIOS) to boot of the first disk and that's where lilo was previously, it appears that either grub wasn't installed or it went to the other drive.
Try changing your BIOS boot sequence and see if you get Grub. It may not boot, but at least you'll know where it went.
In order to fix the bootloader, you can boot from the inatallation CD/DVD but instead of doing the install, there may be a rescue option.
Choose it and if there is no 'Re-install boot loader' option, go to a console.
As the necessary steps, you will probably have to:
- change the root to the actual path of your installation (the console may not be set to the same root as your installation). In Mandriva, for instance, the root is mounted in the /mnt folder, so you need to 'chroot /mnt'
- edit your /etc/lilo.conf to accommodate for your installation. This is fairly complex, so you may have to post the contents of that file.
- run the bootloader by typing 'lilo'. You should see messages like 'Added linux' and so on, for every operatins system that lilo is set to load.
If all goes well, you will be able to boot Linux upon restart.
Poste some details.