Is my ATI 4770 on bottleneck?

Well I'm experiencing issues on FPS with my PC on Aion and I'm not sure if my card is being bottleneck by the CPU, specs are

Intel Core 2 Duo 2.0Ghz
2GB RAM
Windows XP
1280x720 resolution
ATI 4770 with Catalyst 9.9 overclocked
500W PSU

I change the 800x600 to 1280x720 and has no difference on FPS and on some areas it's steady 70-120FPS and no difference either if it's on 800x600 or 1280x720 either on low settings or high, same ammount of FPS.

Though my brother plays the same game on a PC with the following specs:

1660x1050 resolution
AMD Phenom IIx4 2.8 Ghz
4GB RAM
Windows XP
ATI 4850 Catalyst 9.9 overclocked
850W PSU

And I also did the test and his FPS was 30-40 on max on everything and also 30-40 on low and 800x600 with no significant increase what so ever.

My old card Geforce 8500 GT did way better that my ATI 4770, I thought it could be a dud so I RMA it and this is a new one and same experience, I'm still under my return period so I would like to see if it's the game/drivers or if my PC is on bottleneck.

Thanks in advance

Apparently sadly after looking everywhere I found the bos where it came, it's this one

http://www.newegg.com/Product/Prod [...] 6819115014

can it still be overclocked? and what cooler would you recomend?

I have a Intel D946GZis motherboard also if that info is of any help.

This is a decent cooler http://www.newegg.com/Product/Prod [...] %207%20pro

Mactronix

The E8400 is the best C2D processor, I think. Though like people are telling you, you should be able to OC that to 2.8ghz on air.