Don's right, the only way to get PPT to video is to convert the output signal. And as Don said, prices run the full range, and generally, you get what you pay for. You may get some mileage if you have a video card with S-video out, but I'd really recommend something like the Folsom Image Pro or an Extron 405.
Is the audio attached to the PPT already? I'm guessing your client wants to have a "happy-face" slide show set to music put on disc. Am I close? Then it is just a matter of getting the signal to NTSC, and running the audio with it. You shouldn't have any latency issues unsyncing the audio, but watch closely anyway to see if you need to delay the sound a frame or 2.
If there is more detailed text on the PPT, look closely at that, as Don pointed out. Down converting to NTSC will really put the fuzz on small text, so give it a once over and be prepared to beef up some point sizes if need be.
All of this assumes, of course, that you are using an external DVD recorder. If you are looking to do this internally, then unfortunately, I have no knowledge of software that will do that. That in no way implies that it doesn't exist. When we are tasked with this sort of this we run it all as outlined above.
Hope this helped.
Mike