Hard drive (HDD) access has become very slow at times
Before even looking at anything else...
Two antivirus apps on one machine is not good; they fight each other.
Avast is also known to be cripplingly slow, with Sophos not faring much better.

AV-TEST is the closest to an actual 'authority' on the subject. Have a look at their recommendations.

I would lose both those antivirus solutions, then test again temporarily without any AV.