I have a 60Gb main drive and a 20 Gb Secondary.
The main drive has my Windows XP installation on it.
The secondary is partitioned into two other drives.
1 x 2Gb for the Swap File
1 x 18Gb for Backups
The 18Gb Drive has folder like Utilities - which contains copies for programs i use and have downloaded of the net (legally), Drivers - which contains all my drivers for my hardware, Backup - where a program called EZBack-it-up 1.2 click here has been set up to copy My Documents and various other settings to, Patches - which contains software patches i have used, Windows XP CD - copy of my Windows XP CD etc etc
But then again i'm really fussy on how i store stuff on my PC. If i need a program then i know exactly where its going to be....