hello all .. I'm posting what worked for me to fix my monitor issue after upgrading to windows 8.1

I have a 2012 Toshiba laptop/notebook with an AMD Radeon Graphics card and AMD processor. Prior to upgrading to 8.1, I had no problems plugging in my VGA cable and duplicating or extending to a monitor. I could use any of 3 different monitors I have .. an LG HD Flatron, DELL flatscreen and a Phillips flatscreen.

I tried for days upgrading AMD Catalyst drivers, window 8.1 driver/update, considered reverting back to Win 8 .. and many of the forums seemed very helpful .. and one hinted at VGA cable incompatibility (thank you because this got me thinking in the right direction) but nothing worked no matter what monitor I used it remained black even though it seemed that Windows recognized there was a monitor there it just wasn't supported or unknown.

Short answer .. I got a $40 HDMI to VGA adaptor (because the monitor I want to use, the LG, doesn't have an HDMI port) and it worked. There was one small gliche in that the monitor would flash black every 30 seconds. I fixed this by changing the Monitor driver from an Analog based driver to a Digital based driver that just happen to come with the monitor software. So I guess this is the "digital" graphics version of Windows 8 and the analog VGA cables are no longer supported directly. I suppose if your laptop doesn't have a HDMI port you're completely out of luck with Win 8.1.

I hope this helps anyone else who is having these sort of problems.

I was very disappointed that neither AMD nor Microsoft posted this as a possible solution on their support sites.
Cheers !