The only thing that still works is the CPU. I think you are ready to change everything else. Your current configuration is as follows:

CPU 2.40GHz

Motherboard 845PE

Memory 256M

Memory 64M

Now the most basic configuration can basically meet most games on the market:

CPU 3.0GHz 3000+

Motherboard 9 15~945

Memory 5 12M~ 1G

Memory 128M~254M

I hope my answer will satisfy you.