I'm worried by the information in your post that you installed 'a 2nd antivirus'. I hope that doesn't mean that you've got two anti-virus programs running simultaneously. This a well-known recipe for disaster!
Anti-virus programs make changes to your registry. If you run two of them simultaneously, conflicts can occur which can cause unwelcome alterations to the registry. If you've got two such programs running, disable one of them and see if that improves matters. If it doesn't, you might need to consider an 'on-top' re-installation of Windows.
Chris