The E521 BTX motherboard model is Nvidia nforce 6150LE 430 MCP.
You can not get this chipset driver from the official site anymore.
You need to have the third party software to update the drivers for example I use this one:
Uniblue Driver Scanner (please inform me if this software is not functioning properly)
This is not a bad software actually.
This is the full version. You will not regret having this software. Give a try.