you never know what it may have done. too many nasties hide in them. normally if win7 was the original os that came with the computer is all you have to do is to delete the win8 partition then use a utility such as bcdeasy to fix your bootloader. that is the easiest way.
i bought this laptop in another state, it originally had window 7 / partition / bootleg window 8.1,to this day i cant use the 8.1, now the seven got upgraded to a 10 with 40 gigs, the bootleg has 460 gigs that i cant use, i would like to wipe 8.1 out and the partitin without harming what i have on the 10, any ideas please