You could always use a program like Acronis True Image to do a backup of the entire system...and then import/export data files from that to your new install, at your convenience.
That's pretty much the way I approach it.
OTOH, if the reason that you feel a clean install is necessary...is because of malware of any sort...it's probably not a good approach.
Bottom line: You will have to reinstall all applications and you will have to visit the WinUpdate site for at least close to 100 updates which are critical to system security.
Backing Up to External Hard Drives - http://220.127.116.11/search?q=cache:gMdz0...o+DOS&hl=en
Backup Options - http://www.onecomputerguy.com/install/backup.htm
Inside Outlook Express - Files and Settings - The OE Store Folder - http://www.insideoe.com/files/store.htm
The Windows Address Book and your Favorites are 2 other items that you will want to backup, if you do this piecemeal.