IIRC, the HOTU version is 250mb. The HOTU version has no voice, movies, animations, and only very very very low-res effects. The real retail version of FS 2 has three CDs.
You don't have OpenGL. OpenGL is a 3d accelerator, and is required for FSO. If you want, you could try some old builds of FSO that still have Direct 3d compatibility, but they aren't going to look so good. Otherwise, your screwed. You'd have to stick with retail until you get a more recent card.
To find out your graphics card:
1: right click on "my computer"
2: go to manage
3: go to "device manager" in the left box
4: then in the large box on the right, look for "display adapters". It's in there.