having issue of lagging

hi i m having issue with my vaio lagging during the game it was not happening before but now days it happens often so please can anybody help me it happens when i play some online games on facebook and also when i play Commnado Strike force and Age of empires am i having problem with my graphics card or any other issue i m having my config is


i3-380M processor 2.53ghz win 7 home basic (64 bit)
320 GB HDD memory 3 GB
ATI Mobility Radeon HD 5470 512 MB (Dedicated memory)