Have you wondered why you received negative scores from other posters?
Whether someone pays for an antivirus product does not have any bearing (unless you sell them) since Avast Free version is rated MUCH better than MOST of the BIG name pay-too-much for antivirus programs. Malwarebytes is a free anti-malware program that is considered among the best alternate/back up scanner for malware that will run properly with nearly any antivirus program already installed.
There is no indication that the antivirus program is a free one or a poor quality one (not the same thing) so your assumption makes no sense.
Further, there is very little that could tie the OP's problem to their antivirus program, except possibly an infection that is already there. If there is an infection, the LAST thing you want to do is uninstall any antivirus program until the threat is removed.
There is no indication that there is any hard drive problems or errors, so your other suggestion is also off base.
As indicated, if a System Restore does not set things right, a Factory Restore from a Recovery Partition or a Recovery Disk Set back to the original Windows 7 64bit with the original drivers, followed by a full and careful update of Windows and Drivers, is indicated and the best solution.
You have to be a little bit crazy to keep you from going insane.