1. Dont do it unless necessary, it is a bit of work and there is the real risk of something bad happening- remember you will lose EVERYTHING in a format
2. If you do decide to go ahead then be prepared
you will need
1) the windows disk- preferrably the pro version
2) driver disks
i) motherboard
ii) graphics
iii) soundcard- if seperate from motherboard
iv) any other peice of hardware
If you dont have them then download all the latest drivers you require and burn them onto a dvd and keep this handy
3) Installation disks for all the software you need
4) patches for your software - burn these to the same DVD you burned your drivers on
5) Copy all your game patches and savegames and config files to your DVD
6) copy all you important information to your backup drive- all your my documents folder, all photographs , porn etc
7) get in a supply of patience and coffee
8 ) google for a guide, print and keep it handy e.g.
http://howtoformatacomputer.com/format-windows-xp
http://www.kellys-korner-xp.com/xp_setup.htm
or go to library and get a manual, microsoft official manual is excellent but pricey
9) Convince yourself you really really want to do it and after setting bios to make sure your PC will boot from cd drive first, put windows disk in and carry on
10 ) consider partitions when doing the reinstall - I like these for dividing up my drive into logical areas like Operating System; Work; Games; Photographs etc
11 ) Take a backup just after you have a clean system i.e. just windows with updated drivers using ghost
With il2 you can copy the entire folder to your spare drive and copy it onto your new system and it will run ok , with most other software you will have to install it fully onto your new sytem so that the registry is complete
good luck