If the screen is flickering in time with the software that you are running, then yes, definitely, first thing to try is a different power supply. All in all, however, it sounds like this puppy is on its last legs.
If you are running Windows 10 on this board, neither the onboard video adapter nor the onboard Ethernet PHY are support. That is, Intel does not provide drivers for these components. Microsoft provides compatibility drivers that allow these onboard components to be used, but the operation of these drivers is not the best - and, as you have seen, problems abound.
For both of these cases, you can use an add-in Graphics card and a PCIe- or USB-based Ethernet adapter. I have to say though that I consider this throwing good money for bad. That is, you are spending money to purchase these stopgap solutions that will allow this board, memory and processor to continue to be used. This is, for most people, money that could have been used in the purchase of a much newer (and probably much more trouble-free) system. You certainly don't want to be in a situation where the money you spent on the stopgap solutions prevents you from having enough money to replace the system.