Here is the cpu support list, it may also depend on the current version of the bios firmware installed on the motherboard if the phenom ii x4 840 is supported.
I will have a check and see if there are any bios firmware update files that add support for the phenom ii x4 840.
The board states it will only support also a maximum cpu wattage of 200W also.
Click on the link bellow to see the range of cpu`s the board will support, you must have adobe reader to open the document to read installed on your system.
Kareem GT also make a good point, if you have used the same hard drive with windows installed on it on the system does power up and boot windows.
It will not work with the new 970 motherboard.
You will have to do a clean fresh install of windows to get the system to work.
https://us.msi.com/file/test_report/TR19_3193.pdf