NY wrote
Rod Speed wrote

I do PC support for other people as a living, but all my standard
"tricks" have not made much improvement on my own PC: a PC
with loads of free memory shouldn't have times when it hammers
the disk as if it's swapping to page file and its CPU usage on system
(ie not user-initiated) tasks shoots up to nearly 100%. And that's
before I try to do CPU-hungry things like playing HD video.

Running which OS ?

Win 7.

32 or 64 bit ?

AMD E-450 1.7 GHz CPU
6 GB RAM

That's the problem, it will fill that eventually and start swapping.

HDD has about 2 GB free space and is defragmented

Avast (free) anti-virus

I've used MSCONFIG to disable all the Samsung-specific utilities
that came with it. and checked for anything else that gets started
automatically to make sure there's nothing unexpected or unwanted,

The problem is that it uses more than 6GB with that more intensive stuff.