Working on an HP G61 laptop with an AMD Sempron M100 (2.00 GHz), a 64-bit processor, running Windows 7 Home Premium 64-bit.
The computer properties show 4.00GB RAM installed, but only 3.75GB usable.
There is also an integrated graphics card, "AMD M880G with ATI Mobility Radeon 4200."
Just checking out this explanation I found: Why Computer Shows Less RAM than Installed
Why Computer Shows Less RAM than Installed
This is because your computer does not have a dedicated graphics card.
You are using a integrated graphics card built on motherboard which shares memory from the RAM installed.
They can share from 1 MB to 256 MB.
If your computer shows around 1-200 MB less than the RAM installed - its okay, anything more your RAM is not installed properly / working.
Is that right?