I found the solution for getting Tiberium Sun to run on Windows 10.
Follow these steps.
1. go to
http://tore.cnc-comm.com/
2. download the TS_Win8fix.zip
3. Unzip, and copy the files to the game folder (where Game.exe is)
4. Start the game and everything should work fine
I'm playing though the series and this was the only one that did not work on Windows 10 right off the bat. All the others are fine.