Backing up my data before reinstalling my Windows OS?

So basically I need to reinstall Windows 7 because of freezing issue I'm having. I have the Asus G73JH and it had a bunch of issues, but I've managed to whittle it down to really random freezing. It'll freeze no matter what i do, sometimes 4 times a day to once every 2 weeks. Anyway, I have a ton of games i downloaded off of Steam and i have 0% of interest in downloading all those games again. As well as remaking iTunes playlists and such. I have a 1tb external i can use to backup, but i want to know if i use the backup tool Windows what exactly will i get when i restore the backup? Will all my stuff reinstall and will my computer basically be brought back to how it was before the wipe, or will i still have to reinstall junk? I'm installing a professional x64 i bought a while back, so it won't be the home version. Any advice before i make this jump?