Acer 7520z BIOS custom upgrade

Hello there:

first posting, does any forum member have any indepth info on whether a legacy bios can be custom upgraded?

I own an Acer 5720z laptop (2008), the bios is an Insydeh20 rev. 3.0, Acer bin# identity is v1.45, it seems that Acer incorporated a memory limit on the machine. Altho the bios & motherboard recognize 4gig of sodimm, no op/sys will boot above 2gig memory installed. I am hoping that some sort of custom bios with no limitations could be developed to unblock the limit currently in place.

op/sys is win7 64