I've installed Mountain Lion successfully on Acer Aspire 4740G.
These steps that i used to install ML my laptop:
1. Create a Bootable USB Drive Using UniBeast following the instructions of this link:
http://www.tonymacx86.com/61-unibeas...7.html?page=17
2. Download and copy NVenabler_64 (http://www.osx86.net/downloads.php?do=file&id=2048) to S/L/E (hidden) in USB.
3. Delete NV* and GeForce* kexts in S/L/E in USB.
4. Try to boot from USB with "USBBusFix=Yes PCIRootUID=1 GraphicsEnabler=No"
5. After installing successfully, run MultiBeast and check Easy Beast Installation, Miscellaneous->FakeSMC, PS2 Keyboard, CPUNull....
6. Remove USB and use ML.