Boot/Rescue disk
 

Can you make a boot/rescue disk after you have installed Linux. I read you should upgrade your disks but how?

Sure you can. What you have to do depends on your distribution though. Maybe you give some more info ;)

I am running Red Hat 7.1 with Gnome. Also have another box using KDE

redhat used to have a utility called mkbootdisk or mkbootfloppy.

One other possibility is to read the Bootdisk Howto.
http://www.linux.org/docs/ldp/howto/Bootdisk-HOWTO/

I don't know if redhat puts more on their rescue disk than a normal bootdisk though.

Some other good utilities are the gentoo linux stage one installer. It's a nice iso around 16MB wich contains quite a few utilities you'd need for a rescue mission. It also doesn't contain a ramdisk with an installer so you could pass root=/dev/yourrootpartition as a parameter to lilo to boot your system in case you destroyed your bootloader. It doesn't work too well though if redhat doesn't use devfs. You can always boot that disk normally though and mount your root disk and chroot to it.

mount /dev/yourrootdisk /somedir
chroot /somedir

Then you see the base of your distribution. You should be able to repair most things.

Then exit from chroot, unmount your rootpartition and reboot.