I have an Inspiron 620 (Mid 2011) as well and I let the Windows 10 upgrade run - not realizing that I needed to check with Dell as the Windows 10 checkup said it will work...

Once it finished the immediate problem was obvious: the video card (AMD HD6450) drivers didn't work and I was looking at an oddly shaped screen...

After looking around, removing all drivers, trying the AMD catalyst drivers for the specific card and OS as well as their older, beta ones (from Win 8.1) - nothing has worked... The device manager says: "Windows has stopped this device because it has reported problems. (Code 43)"

I'm at my wits end... at this point I'll switch back (god help me) to Windows 7...

I'm trying the Microsoft Answer desk as a last ditch effort