I was having issues recently with my original 6GB RAM. Lag, and max capacity of processing, since Windows 10 install and most recently with the newer updates
The Manufacturers recommendation was maximum 8GB DDR (4 x 2GB) which is what I installed.
Now the PC only recognises 4GB (2 x 2GB) out of the of 8GB total.
I have looked at the BIOS and it only sees 4GB.
I have looked for a BIOS update and nothing since 2010.