RE: Dell Inspiron 1525 internal microphone
I just solved this issue.
Search DELL site for drivers (tab "Help and Support") by "92HD73C1".
It finds about 30 entries for Alienware laptops, but one entry mentions Inspiron too: http://www.dell.com/support/home/us/en/19/Drivers/DriversDetails?driverId=NWM04
IDT 92HD73C1 Audio Driver
Consider A15, this is BIOS version I presume.
I had A11 so I decided to upgrade to the latest A17 before installing this driver.
Then I installed driver package R226903.exe and my microphone array works well in Win 7 x64 on Inspiron 1525 now.
Just to mention, there is later version of this driver to download: http://www.dell.com/support/home/us/en/19/Drivers/DriversDetails?driverId=G11FC
However the description contains no word about Inspiron, BIOS version is A18 i.e. greater that the latest one available for Inspiron, and when I tested it on A11 BIOS it did not work. I decided to not re-test after I upgraded BIOS to A17 and then installed R226903... never touch a running system, you know.