First make a folder in your windows 8 called Old computer or Win7 or whatever you want.
make a shortcut to that folder on your new Win 8 desktop
open that folder, if you grab to top left of the title bar and drag it allll the way right it will situate itself on the right half of your screen
goto computer doubleclick the windows 7 drive
left click and drag the upper right side of that folders pane and drag it alllll the way left to fill the left half of the screen
doubleclick users
find the usernames you want to save and drag it into the folder you just created on the right
This will copy pictures, music, videos, settings, etc...
Its best to copy it all then filter out what you dont want..
After all is done scan your Win 7 drive for errors and viruses, if it finds errors or viruses and fixes them, your system may boot again when you reinstall it..
Dont delete anything until you know everything you want is in your new computers backup/win7 folder
Once all is done we can work on fixing your Win7..
Good luck..