Check to see if RAM is wobbly - there is a notch on the RAM stick but it is not in the center, so it can only be inserted one way. Pressing firmly on both ends will cause the clasps on both ends to click shut. Usually if RAM is not inserted properly machine will not boot, but maybe yours is different.
Since Ethernet is part of the mobo, you will have buy a $15 card if it is faulty.
Since Ethernet is part of the mobo, you will have buy a $15 card if it is faulty.