Yep, I was able to make the reservation as well, although I ended up downloading an .ISO and upgrading from DVD after all.
https://www.microsoft.com/en-us/softwar ... /windows10Anyway, you'll get a barebones MS video driver, dated 2006... so no GPGPU and very few - if any - HW acceleration features utilized. Plus a yellow exclamation mark in Device Manager, indicating a problem or limited functionality. I figured I'll just disable the iGPU (equivalent of 9400GT) to avoid complications. At least I gained 512MB extra RAM from that. The GPU lag is tolerable in most of my use cases, so I can make do without the iGPU. To recap, you can get WinX up and running - or crouched and limping, if you prefer - with a pre-Fermi, but most likely you won't be happy with the results.
There was a pleasant surprise after upgrading from Win7 - the upgrade cleaned up a few years worth of bloat. I gained over 5GB free space on my C: drive after running Disk Cleanup of system files! So far, the only app having problems after the upgrade was an old CyberLink Blu-ray Disc Suite which I don't miss much at the moment. So I don't think I will be rolling back to Win7, as long as these two remain the only problems.
Another caveat, conveniently published 07/29/2015 12:29 AM:
http://nvidia.custhelp.com/app/answers/ ... phics-cardMaxwell and Kepler GPU architectures support Windows 10 WDDM 2.0 mode with support for Fermi coming at a later date. At the time of Windows 10 launch, the GeForce Fermi architecture operates in WDDM 1.3 mode. Since it is not possible to load both NVIDIA WDDM 2.0 and 1.3 mode drivers at the same time, you will not be able to mix Fermi class GPU(s) with Kepler/Maxwell class GPUs.