I installed XP on C.
Then, I moved the "My Documents" folder to D.
I moved the IE favorites to the "My Documents" folder.
I have moved my emails to the "My Documents" folder.
When I install a program, I install it on D.
Having installed all my favorite programs and utilities, I have made an image of C.
Now, whenever I want, I can restore the image in 3 minutes and get a fresh new operating system with all my programs working.
C is only 3.7GB. The image size is only 1GB.
The advantages of this setup:
1- C is relatively small and easy to backup and restore.
2- Re-installing the OS does not require a full backup of all the data on the hard drive.
3- I can boot into another primary partition (after hiding the first one) and still use all the programs and "My Documents" on D.
The disadvantage of this setup is that if I install a program now and then, restore the OS, the new installed program may not work anymore and require re-install. So, you need know what you are doing if you do this.