Window 8.1? Could you install 1405 and cold boot (shutdown /p). After booting into the OS again, you should see Generic Adapter in Device Manager. Then try installing Intel® Download Center (32 or 64)? Make sure you perform cold boot between uninstall and re-install steps.
Brilliant. Thank you!
did this work for you? Which form factor does your 7260 Card have? Mini-PCIe oder NGFF/M.2?