Yes, this model can support AM3 CPU. The detail support CPU list. Please refer to this model's CPU support list available at  web.
Please refer to Product page - CPU tag

Please double check the following situation.

1. If there is any software or hardware updated before such symptom, plesae recover the system back to original status and then check it again.
2. Make sure all the heat sink and cooler installed well.
3. Check the status of all other peripherals including PSU, CPU, RAM, HDD,...etc.
4. Please update the latest BIOS/ drivers from website.
http://www.ecs.com.tw/ECSWebSite/Product/Product_Detail.aspx?DetailID=988&CategoryID=1&MenuID=20&LanID=0#fragment-Download

If all above does not work, please contact with your seller for RMA service.

http://www.ecs.com.tw/ECSWebSite/W2B/WhereToBuy.aspx?MenuID=5&LanID=0&AreaID=5&CountryID=61&TabID=1&ln=1

Please download the drivers from the link below.

http://www.ecs.com.tw/ECSWebSite/Product/Product_Detail.aspx?DetailID=857&CategoryID=1&DetailName=Feature&MenuID=20&LanID=0#Fragment-Download

The front panel audio header allows users to install auxiliary front-oriented microphone and line-out ports for easier access.

The maximum HDD size we tested is 750GB, the below table has listed the HDD that ECS tested and qualified.

No, you can not update BIOS between different PCB verision. Before flashing BIOS, please pay attention to model name and PCB version again. This can prevent the mistake and lead to MB boot failed.

RAID stands for Redundant Array of Independent Disks. It  is a technology that provides increased storage reliability. This model can support RAID0, RAID1, RAID0+1, RAID5 configuration.

For more information, please refer to,
http://en.wikipedia.org/wiki/Computer_data_storage

Please download the drivers from the link below.

http://www.ecs.com.tw/ECSWebSite/Product/Product_Detail.aspx?DetailID=988&CategoryID=1&MenuID=20&LanID=0#fragment-Download

The model comes with one PCI-Express slot, is fully compliant to the PCI-Express Base Specification Revision 1.1. The graphics card support table has listed the graphics cards that ECS had tested and qualified.

Please download Windows 7 drivers for this model from the following website.

It is normal. Due to PC architectural requirements such as OS, applications and  memory shared for onboard graphics, the left available physical memory will be various and less than total physical memory.