Game won't open to a full screen. How can i get it zoomed to fit my full screen

Command & Conquer 1, Red Alert 1 and Tiberian Sun have all been upgraded with community-created unofficial patches that fix a lot of their bugs and compatibility problems. You can find them here:

Command & Conquer 1:

• Nyerguds' C&C95 v1.06c revision 3 patch (note that this one might need some additional tweaking on Win10. Last I tried, I needed to put it on WinXP SP3, and bizarely enough, had to disable the "run as administrator" for it to work.)

Red Alert 1:

• Funkyfr3sh's automatic Red Alert 1 patcher/installer

Tiberian Sun:

• Funkyfr3sh's Tiberian Sun patch

For RA2... there's an option in the compatibility settings called "disable display scaling on high DPI settings". Apparently  it affects that. Besides that, I also advise installing the graphics system patch DDWrapper; it's known to solve a lot of issue on RA2. Download the zip file and extract "ddraw.dll" and "aqrit.cfg" into your game folder. Then, open the configuration file "aqrit.cfg" in Notepad, change the "ForceDirectDrawEmulation" option to 1, save the file, and the game should work.

For the games after RA2, I sincerely doubt you'll have that problem, since, unlike the older generations, those games have scaling UIs that adapt to your game resolution. So to fix those games, just set them to your native resolution. There are sticky topics around here that'll help you with creating their config files.