The only way you can overclock a IGP is too overclock the entire system, the CPU and RAM so that more Graphics information can be processed. It is not worth the trouble, invest in a stand alone card GF4MX won't be able to run much.....
The Motherboard you have also doesn't look like it would overclock very well so check NewEgg for a cheap card... Do you have an idea for a new card?
There are only Two things in life i regret doing... 1. Selling my Soul for Cash.... 2. Buying a Compaq.... I should have kept the Cash, huh.