Splinter Cell Conviction Graphics Help Needed?

Hello,
I have been playing Splinter Cell Conviction for a long time now,
My problem is I have been playing it with lags.
My system is:
Pentium D 3.0GHz processor (Not Dual Core)
2GB DDR2 RAM
NVIDIA 7200GS 64bit 256MB Graphics Card (Latest Driver updated)
Windows 7

I know this PC is way lower than requirements and the graphics card is not even supported.
But, since I don't play any games other than this one. So I don't want to upgrade my PC for this game only.

I have tried making it faster by the following ways:
i) Edited all .ini files in the game directory and C:\ProgramData\Ubisoft\Conviction (Disabled shadows).
ii) Using Game Booster 3.
iii) Upgraded to the patches 1.03 (1.04 makes graphics worst)
iv) Lowered down all the graphics for eg; picture quality etc from NVIDIA specific application setting.
v) I'm using MSI Afterburner and overclocked my core clock from 450 MHz to 585 MHz (Max) and memory clock from 532 MHz to 695 MHz (Max).

Nonetheless, it made my game alot faster but it just went from 8 FPS to 11-15 FPS Max even if I'm running it on the lowest possible settings at 640x480 resolution.

Now, I have tried using custom resolution at 320x240. The game ran adequately fast but the textures are not running. I can't see any walls, my character or anythings just plain black screen and a few textures. I was only able to play through sonar goggles so it's useless.

Now my question is, Is there any way to make the textures visible at 320x240 resolution or any lower resolution than 640x480?
OR, Anyway by patching it with low graphics mod or deleting any stuff from the game environment that could make it any faster?

This will be a bit crazy but I love this game and I just can't upgrade my PC for it. I would be so glad to receive your advice on this one. Thank you in advance.
P.S I have been able to patch my game to 1.04 and its running as smooth as 1.03. I did more editing in the .ini files but still the FPS is at the same point where it was at 1.03 patch.