IIRC Red Alert came with a DOS version and a DirectX 3 version for Windows 95
At the time I had only an old 486 with a 500MB disk under DOS, and I played this game quite extensively.
I even remember cutting the sound to gain a few FPS, which enabled me to go from "unplayable" to "barely usable" ^^.
Same applies for Tiberian Sun. GDI and NOD CD's.
I have them all via the "The Command & Conquer Collection" released back in 2003.
Source:
Red Alert: https://i.imgur.com/xD7j08b.jpg
Tiberian Sun: https://i.imgur.com/xD7j08b.jpg
This continued with Tiberian Sun and Red Alert 2. Generals came on two CDs but it used the “install disc” + “play disc” system rather than the “lend one to a friend” model used previously. Then CNC3 was released on a single DVD.