I've struggled with the simplest of tasks, exporting PPTs at enough resolution so they don't look like crud and have enough resolution to be usefull for panning etc. Well I just stumbled upon a MSDN article that explains how to fix the problem.
Read it
here.
This does involve editing the registry but nothing too scary and it does friggin work. Once you've done the Regedit just open PPT and Save As .jpg or .png and in my case having set the thing to 300dpi I get very usefully sized slides. The thing is, by default PPT does it's graphics export at 96dpi, no wonder the results look so bad.
Bob.