I would not delete or overwrite your Windows 7 as Win8 may do if you run it from within Windows 7.
What I would instead do is try virtualizing it and if that is not successful, shrink C partition to install it as a Dual Boot as I have done and not returned to Windows 7 since.
You'll need to download the ISO from boobah's link above, burn it to DVD using WIndows Image Burner, then boot it to install to the space you shrank from C.