Thax for the replies DigitalHermit and VincentP. I'm not a hard core game player. I just play medium games like NFS Mostwanted, Counter Strike etc., They used to run well in my previous dell 1558 laptop (i3 1st gen, 4gb ddr3 ram, intel hd graphics). But I gave it to my sister and using this old PC. To my surprise it couldn't handle NFSMW smoothly. I don't know if it is because of lesser RAM, or the processor. Plz go through the below snapshots of the specifications of my desktop and tell me if increasing RAM will solve the problem or do I need to install some mediocre graphic card. Thanx in advance.
http://imageshack.com/i/b5fukgj
https://imageshack.com/i/fv5w69j
https://imageshack.com/i/f70l9mj
https://imageshack.com/i/eudpy1j
https://imageshack.com/i/nd8yd2j