Nvida GT 430 advice needed

[gadget_freak2]

i had bought an asus mother board
specifications:
Board: ASUSTeK Computer INC. P7H55-M LX X.0x
Serial Number: MF70B1G07505693
Bus Clock: 133 megahertz
BIOS: American Megatrends Inc. 0402 10/29/2010
/
i added a graphic card :
Nvidia gt 430
and lastly intel core i3 as the processor
it wirked fine for over an year but now it has been lagging on games and also some of the videos get pixelated
its not like it was not working but it is not working as good as it was at the start
for now i cannot change the motherboard as it is compatible for i5 and i7 so i was thinking to buy a new graphic card.
my question is is it really necessary or it can be fixed by some video codex or other cleaner tool softwwares.

there is also a dilemma about wether i should change my gpu or cpu

if i have to change anything could you please suggest some good graphic card that can be compatible with my present mother board.
thanks (advance)

P.s my price range is maximum $110

 

[grumbledook]

Are your drivers up to date?