System lag?

I have an older system - it seem to have lag issues when I game and was hoping for some help.

I have
win 7 64 bit
GA-MA790X-UD4P
Phenom 2 x4 805 processor
Hitachi 721010sla330
8 Gb DDr2 800 I think



WINDOWS 7 Score info
Subscore

Processor AMD Phenom(tm) II X4 805 Processor 7.1
Memory (RAM) 8.00 GB 7.3
Graphics NVIDIA GeForce 9800 GT 6.7
Gaming graphics 4095 MB Total available graphics memory 6.7
Primary hard disk 797GB Free (931GB Total) 5.9


Windows 7 Professional


Graphics  
Display adapter type NVIDIA GeForce 9800 GT  
Total available graphics memory 4095 MB        
Dedicated graphics memory 512 MB        
Dedicated system memory 0 MB       
Shared system memory 3583 MB
Display adapter driver version 8.17.12.7533  
Primary monitor resolution 1920x1080  
DirectX version DirectX 10
Network   Realtek RTL8168C(P)/8111C