Ok, I didnt know I could do this, but it works!
1. Save youre files to a UsB
2. Open it up on youre computer with Hex Editor
3. Where it says "Welcome to Modern Warfare 2" Type over that at the beginning. And for each letter, Highlight the letter and Right Click
4. Where it says 'Hex Value' change the value to one of these to coresspond with the button you want.
0E = START
0F = SELECT
10 = L3
11 = R3
12 = L2
13 = R2
05 = L1
06 = R1
14 = DPAD UP
15 = DPAD DOWN
16 = DPAD LEFT
17 = DPAD RIGHT
01 = X
02 = O
03 = []
04 = TRIANGLE
5. Once done, save the file.
6. Unplug your USB and put it in your Ps3.
7. Open up the USB and overwrite the file.
8. Start up Mw2 and look at the MoTD at the bottom