Your original install was missing the older DirectX v9.0c files, but you're fine now. As for the screen size (resolution), if you will always play the game with the computer attached to the TV, you will want to match that in the game. Since you mention it being a 1080p Plasma, I will guess that yours is like mine, and has a "Native" resolution of 1920x1080, which is a 16:9 widescreen.
If you right-click on your Windows desktop, and choose "Display Settings" in Win10, and you'll see a drop-down box for "Resolution" (unless you've got Win7, then there's a choice for that directly from the right-click on the desktop). If you don't see "1920x1080 (recommended)" in that window, then set it to that. If you used the "Multiple Displays" and "Advanced Settings" section to set things up, you should go through that area. My Win10 laptop can connect to our 1080p TV via HDMI, and I've got it set through that "automatically", that when I plug in the HDMI cable, it picks up the 1080p TV right off, and changes the desktop settings to match. Very nice.
Once you have the display set to what you want on the Windows side, open the game and get to the main menu. From there, choose the "Options" and then "Graphic Settings" choices. At the top of the next page is the "Game Resolution" drop-down box. Generally speaking, the higher resolutions are towards the bottom of the list, but they sometimes won't show the correct ones, unless you've set the display correctly in Windows prior to starting the game. You should find a "1920x1080" setting or two in there. You might have a choice for a 40mHz and a 60mHz setting, but mine only shows a 60mHz choice. I don't know why, since my monitor does refresh at 40, but functions OK at the 60 setting, apparently just ignoring the "push" to go higher. You'll have to re-start the game for the changes to take effect after you "Apply Settings", "Are you sure?", "OK" you're way back out.
