Using two different GFX cards on one machine

[Omanes Alexandrapolites]

Hi guys,
As you may know, I bought a new PC a few months ago. Only problem is that it refuses to play M:TW, S:TW or a few other members of my older collection. This could have been made bearable by my laptop allowing this to happen, but, most unfortunately, it refuses to run the older drivers which could enable compatibility.

I must have completely lost it, but, if what I want to do is possible, I'm going to try and buy a second hand Nvida Geforce 2, and ram it into my free AGP slot on my motherboard.

As you may expect, there is a snag - I don't want to have to sacrifice my 8800 GTX to be able to do this. I have read stories on the internet of laptops having two entirely different graphics cards together, with a choice over which one to use on boot, but nothing about PCs enabling this feature.

So, may I ask, is there the possibility of having two cards run on one machine, and have the ability to select which one the owner wishes to use on boot?

All contribution appreciated, thanks!