I think the "American Megatrend" indicates the manufacturer of BIOS, not the motherboard.
ZX probably means "Zebronics". I've browsed through their website, and found this page:
http://www.zebronics.com/productDetails.php?id=26
However, as far as the little picture allows to read, it's not the exact same type that you have. If you click on the "Support" tab below the image, there's a link to a contact page, maybe worth considering to use it:
http://zebronics.com/contactus.php
When I click on the word "Support" on the main horizontal menu of the webpage, I can see a "Drivers downloads" link. The "Select product" list doesn't contain motherboards, so I click on the "click here" link below:
http://www.zebronics.info/downloads
Pick the motherboard directory:
http://www.zebronics.info/downloads/motherboard/
There are three directories with "945" in the name, my penny is on this one:
http://www.zebronics.info/downloads/motherboard/945_478/
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