Malware is installed by clueless users, it's not something that comes out of nowhere. Run as admin and click on "yes" on every possible warning and you'll get just that. Malware isn't mandatory.

I managed +- 100 computers in a university lab. Only reinstalled once, a computer with bad memory chips which were corrupting data, so corrupted windows and antivirus updates had caused a real nightmare. I don't see why reinstalling should help. If you have a problem, it often has a cause. If you reinstall, there is a big probability that you'll have the same problems, because you'll probably do the same things. Understand your problems and their causes and solve them, instead of wiping everything just to do the same thing over and over again. Corrupted installations? Run as admin and don't update, and your box will be corrupted. Don't do it and it probably won't. If you don't run as root on linux, why do it in windows? You don't have to, I didn't for years and have always had clean computers with fixable problems.