I will make sure to give you guys some pictures of this beast! oh the dread of re downloading my games again though haha, I'm still shocked about this!
If your games are on Steam use the backup feature and save them to a hard drive, and then reinstall them from the backup.
Open Steam
Right click on the game
Click Backup Game Files and choose the games you want to backup that are installed.
Next box to appear will give a option of where to save them to, it can be a hdd, usb hdd or even networked computers iirc.
Choose the format but it will be best to choose DVD as that way, you can also burn them to disc if you want.
Click next and then it will back them up.
When you install Steam on the new pc install Steam
Open Steam and click Steam in the top left corner on the menu bar
Click Backup and restore games
Navigate to the folder with the backups and choose each game
It will then reinstall them from the backups and then the only downloads you will need to do will be updates and DLC etc.
Hope that saves you abit of time.