Have a LG L194WT 1440x900 display but cannot set that resolyution - max is 1280 x 1024 after upgrade from Windows 8 to 8.1

Often, when an Operating system upgrade has taken place in a computer, the driver you had running your display may need to be updated to match the new Operating system; in your case, the change from Windows 8 to 8.1.

Go into your "Control Panel" then open your "Device Manager"
>In that list, click on the little arrow to the left of "Monitors" to see your monitor listed below.
>Double click on the listed monitor, to open your monitor properties window.
>At the top of that new window are the tabs to choose from, to view the different opttions --- Click on the "Drivers" tab...
>Then in that window, you will click on the "Update Driver" button.
>Then click on the first choice, to: "Search automatically for updated driver software"
It should do a search to see if there is an updated driver for your monitor that will work better with the Windows 8.1 settings... Be patient; it may take a couple minutes to complete it's search and install (if needed)
>Once your computer has either checked and updated your driver, or said that the driver is up to date, click "OK" to exit that.

While you're in your "Device Manager" also do the same for your "Display Adapters"

Once you have checked to be sure your drivers are the most up to date ones for your monitor and Operating system to be able to work smoothly together, open your Display settings...
>"Control Panel"
>"Display"
>Then click "Resolution" or "Adjust resolution" in the list of choices on the left side of that window.
>Then click "Advanced Settings"
>Then click the "Monitor" Tab at the top of that window.
>Then under "Colors" be sure that "True Color (32 bit)" is chosen.
>>If it was reset by the upgrade to "High Color (16 bit)" and you have now changed it to the "True Color (32 bit)" setting, that may now enable you to adjust your resolution to the 1440 x 900 again.
>Once done in there, click "OK" to exit that.

After you have completed all the steps I have listed above, please restart your computer to see if your resolution issue has been adjusted accordingly..

I hope that resolves your issue... If not, then you may have to refer to the menu button controls on your monitor itself:
LG L194WT BF User Manual Page 20
Pages 20 (bottom symptom checker in list) to page 25 will walk you through your monitor's menu adjustments at the physical monitor.

GOOD LUCK HUN! Hope I was able to help =)

There are two possible issues that can cause this:

1. The graphics adapter driver is not correct (using default VGA)
2. The OS doesn't recognize the monitor's resolution capability.