OpenGL newbie seeks help!

Hey /prog/, I'm writing a cross-platform OpenGL application which does some off-screen rendering. I've found two ways of doing that - with pbuffers and with FBOs, the latter is preferable. I want old videocards to be supported too.
Now tell me, which technique should I use? Do the older videocards support FBO? Do they support pbuffers?
Thanks.

>>18
I would argue that the present is nicer because it lets you do more and many things (i.e. scrolling, blending, rotozoom, 3D, etc.) are easier.
First Quake did this all without any problem. Besides, all this graphics bloat just distract programmers from gameplay. A good game, like Dwarf Fortress, doesnt need graphics at all.