High threat trojans one scan then next scan none at all??

Hello.

I have just scanned my computer about 30 minutes ago with the free version, and I brushed up on my knowledge on the viruses I had, but when I rescanned, a chilling result came up with 0 threats detected other than not being protected.  All my other antivirus programs can't find any of them either. Some of them were HKEY which I don't think could automatically hide somehow after being scanned, and the other five were in my program files.

I'm very disturbed on this issue and worried for my computer, permenant damage, privacy and nasty scam tricks.

 

Can anyone please, please give me some suggestions, ideas, support or feedback on this strange issue?

 

Thank you.