mettelus
That would affect my GTX 580 as well. Hmmm, can you redeem Win10 but not install it?
I installed the Windows 10 preview and my NVidia 550 Ti works great with the latest Nvidia driver.
Also, from what I understand, if you reserve your Windows 10 free upgrade, it will automatically download to your computer. It will notify you when it is ready to be installed. You don't have to install it right away. However, you won't get your new CD Key until you do install it, so I would assume that you would have to install it before the deadline of the free upgrade in July, 2016. That's just an assumption on my part.