I suspect that I have malware on my computer which cannot be detected by my antivirus software. For some time I wanted to “clean up” my laptop anyway and now I would like to do a complete factory reset. In order to do this, I would like to back-up all my files externally and then move the ones I need onto my newly reset laptop. Would a complete reset automatically remove all the malware/viruses that I possibly have? Any other tips for how best to do this?
Depends.
The most sure way would be to use a known good computer to make a USB or CD of a tool like gPartED or DBAN and nuke your computer’s hard drive, then use that known good computer to make a Windows installer. You might also upgrade the BIOS while the drive is blank to remove anything that is persisting there too. You will loose all the data on the system, and you can’t trust anything from that system.
You do all this correctly, and you might be alright.
This is the problem when you have something that you don’t know what is, that “cannot be detected”, if you can’t identify it, you don’t know what it’s characteristics are, what tricks it might use, where it may hide.