Ouch, that CPU might hold you back on reaching the full potential of the new 560Ti.....
http://www.newegg.com/Product/Product.aspx?Item=N82E16819115005
BUT, even IF the CPU is holding thing back the 560Ti should be at least as fast as the old 8800.
We need to compare apples to apples:
- First thing that come to mind is DX10 (8800 card) vs DX11 (new card). What game are you running? Try to set it to DX9, DX10, and then DX11 and check the FPS with FRAPs at each setting. How does that compare to your old 8800 ?
- Then there are the games detail settings & resolution; are they set the SAME as when you were using the 8800 GT ?
The 560Ti should mop the floor with the 8800, we just need to test with all the settings the same so we can tell if the 560Ti is working properly...
Thanks for the system details, Win7 64 bit version & 4Gb RAM eliminates a few things (you're likely not thrashing due to too little RAM).