One of the greatest applications that I don't think enough people use is Dropbox. Always have your stuff when you need it with Dropbox. 2GB account is free!. Using dropbox you can install the portable applications you use on multiple computers or just want recovery from reformats. Dropbox syncs to their cloud servers and stores your files.

Install Dropbox.
Set the directory where you want your files to sync to or accept the default.
Now in your user folder you will see C:\Documents and Settings\{USERNAME}\Dropbox or C:\Users\{USERNAME}\Dropbox
Create a folder for portable apps _APPS

This is where you will install the apps you want. I like to use portableapps.com application or you can manually install portable apps. WinRAR, Notepad++, Chrome, Firefox, CCleaner, etc.

All you have to do for a fresh install is create the shortcuts from the _APPS dir for that program.