I a bit of a noob myself, but since noone else has replied I'll give it a go
I had two machines, one had KDE on it, and the other had Gnome. Now, I want to put both the hard drives in one machine. I have already recompiled the kernel for the hard drive that I want to install. But I did so by temporarily disconnecting the existing harddrive.Now, I want to have both on-line, with an option to boot either of the two. I have grubinstalled at present.
Edit the menu.lst to include options for both kernels. Use the man pages to help on this. You just need to tell grub to boot from a different 'root=' using hd1 instead of hd0. You could try reinstalling Grub (grub-install <device> I think) which will probably do all the hard work for you. It did for me with different installs (32 and 64 bit) on separate partitions.
my other question is how to mount various drives (root, home, usr etc...) Because when booting from one hdd, i would need only the home partition of the other hdd. Anyedit your /etc/fstab/ as root (or use su/sudo) with you favourite text editor. Insert an extra line for /dev/hdXY where X is the letter of the 'other' HDD and Y is the partition number for home on the other HDD. Use a mount point like /otherhome but the rest of the details can be the same as your /home information. Save and $mount /dev/hdXY. Repeat for the other install when required.suggestions how to do this..
HTH Wackojacko