How do i remove "Ads by Testpid"

[Irish_ish]

Last week my brother said he found a place to download a flash game he really like and did it. I chasied him for downloading stuff on my oc without asking and he apppologised. Then i scanned it with norton and it said only 5 users had it but was otherwise fine. Skip forward to this morniing and googles search engine keeps switing to yahoo randomly, and now at the start of every search has like 5 ads from tespid. I have deleted every program i dont know what it does deleted the files that were downloaded and ran nortons pc scan. Nothing is working and I need to know if i just need to back up my importaint shit and nuke my pc. Can anybidy help?

[Needfuldoer]

Do a full scan with MalwareBytes, and check Add/Remove Programs and your browser extensions for anything that looks sketchy.