My grandfathers old DV6 6c77 HP laptop had lot's of issues with the Intel GPU and AMD 7400m on Windows 8.1, even his new HP ENVY 17-k251na laptop with a Intel GPU and Geforce 850M had issues, they really didn't like to play together.
Could never get both to work together properly on either laptop. I upgraded both to 10 Pro and the drivers that 10 installed worked perfectly on both laptops. I can now use either GPU's at will. Windows 10 is fantastic, no issues with it at all.
http://www.notebookcheck.net/AMD-Radeon-HD-7470M.67752.0.html
According to this the 7470M is a rebranded 6490M, which could be why. Have you tried the 15.7.1 drivers on the AMD website to see if they help?
upgraded my laptop (intel hd4000 + 970m) to win10 and it's working fine.
It looks like that laptop uses fixed mode for switchable graphics, which 10 oddly hates. Is there an option in BIOS to disable the Intel?
if this reply was for me, then no there is nothing in the bios i can turn on/off that will affect the display adaptors.
the only was i can turn off the dell hd3000 adaptor is in the properties tab of it. My bios is version a12
Yup that reply was to you, forgot to quote.
Sadly there's not much you can do then...
I suppose you can rant on here and hope AMD will come up with a fix soon: https://community.amd.com/docs/DOC-1314?q=switch