before i resort to reinstalling windows 7, i would like to but i can't find some decent .iso (link me some good torrent if you can)

my pc randomly freezes for a while now, my sibling installed a win7 theme but it also came up without shady apps like free antivirus and stuff but i managed to uninstall it i dont know if it has remains but i don't know how to remove it manually

i was hoping if i can fix this problem without resorting to reinstallation