If the 15.7 drivers dont work, try the beta 16.2
Before trying these again, here is what I would do.
download DDU (display driver uninstaller)
disconnect from internet. either disable the network interface, unplug cable, or remove wifi card, depending your situation.
restart the computer into safemode, run the DDU utility in safemode. find the options that clear the file folders as well, bubble on right when software is loaded up, in advanced options.
the disconnect from internet prevents windows from trying its own driver.
If windows 10, you may have to research the ability to prevent windows from attempting its own driver install.
This method worked flawlessly helping a buddy install my old 7870 card. Was having same issue as you.