You pick out some benchmark app then run that as-is. Don't tinker yet.

Save those numbers then end that suspect items and run it again to see if that program was the culprit.

There are no safe sites today save maybe Ninite. All can cause trouble. Far fetched you say? What if your PC was on the verge of failing or had a barely working heatsink fan. The stress of testing could cause a failure so for me to write it's OK is not OK.

As to checking for common unwanted software, why not Grif's list at:
http://forums.cnet.com/7726-6122_102-5509131.html?tag=posts;msg5509131
Bob