Hi Reloading Windows requires some planning and also some install disks.
First think is to run belarc advisor
http://www.belarc.com/free_download.htmlCheck that report that you have your Windows 7 key and Office keys there are other programs that will give you this info but this also lists your hardware that if you don't want to run the next program will help you get your info to download drivers.
Run Double driver from here
http://www.boozet.org/dd.htmAnd use that to backup your drivers.
Do you know all the passwords for email, skpe and websites if not you will need a program called SIW
https://www.gtopala.com/siw/buy_other.php download the trial version, Go to secrets left hand column and copy off the user names and passwords for sites and email accounts
Now do you have a dvd with the same version of windows 7 you found with Belarc Advisor ?
Do you have an office DVD the same ?
Also it is a good idea to copy off your downloads folder, any import documents etc
If you are not going to do a full backup then at least have a look at "windows easy transfer" , best to run that program from the windows 7 DVD as with windows updates this program has changed and if you use a different version it may not restore.
Seems like a lot of things to do but once you reinstall, the computer is back to the way it was before you started using it everything gone.
I always do a full backup with Todo backup or replace the drive with a new one and install windows onto the new drive.
I hope this makes sense