You might not be able to increase much performance, nor oc it much if at all.
1)Your mobo has onboard video and is probably not very good for oc.
2)Your ram, don't know brand etc and why is it single, why only 512.
3)your ram and gpu are holding you back and there is no way you can play todays latest games, no way. Even if you upgrade one of the two, you will still not be able to play.
4)Format
Install most suitable drivers for the config
Set all settings eg: nvidia control panel at highest performance
Tweak all in game settings to deliver the performance you need, some/many games may be 640*480 lowest or even unplayable.
Regualr defrag
Use tweak utilities.
Practically, gaming without upgrading it is only possible if you want to play games which were released in 2002-2004 or older.
