Lag with video games

I don't get it I've tried everything people have told me here what else is there its very frustrating.

Can anything else be done?

I have the same problem with fear combat.
My problem come from the mouse (G9) and keyboard (G15) of logitech.
Do you have any of the 2 devices;

I have a wireless mouse from logitech

I think, could just be microsoft

No one knows?

have u checked for overheating?

I already did somewhere. I have:
Dell, I stated with Vista but had a free uprade
IDT Audio
Nvidia Geforce 8400 G I think, the graphics are fie
Intel Duo Core Prossesors
2814 RAM Free
What else?

If you have updated drivers, DirectX, the only things left are software conflicts and hardware - are your temperatures running hot? What antivirus?