Microsoft Windows 10 free update. Yeah. It told me in its cheery way that my Dell Optiplex 330 system with Windows 7 Pro and all my apps and devices were fully compatible and assured me we were "good to go" and there were no issues.
However, immediately after the upgrade three very important little things didn't work: Wi-Fi adapter, wireless keyboard driver and monitor driver. That's right, screen, keyboard and internet. The only thing that worked was the wireless mouse. And that was only because it was a recent replacement one that came with the keyboard. If that hadn't worked I would not be typing this now.
If the thing that connects you to the internet, in my case a USB wi-fi gizmo, doesn't work after the upgrade, it's not much good it trying to look for updated drivers - because it can't connect. If it had only been the keyboard I would have found a way around it, but the wif-fi adapter was the killer. The messages I got from "Troubleshooting" were:
Broadcom Bluetooth 3.0 USB adapter driver has a problem
D-Link micro USB driver has a problem
Video controller has a problem. (The display was wonky).
I found my way through "Troubleshooting" to "Return to Windows 7 (available for one month only)". At one point it asked me to describe the problem but I couldn't type anything - wireless keyboard, remember? After several hours my system is back to how it started, i.e. working fine.
I won't be signing up for the free upgrade again. You might be lucky but I wasn't.