universal screener for corp. America via a Mac

I had to prepare some small screen videos to send to a big Silicon Valley internet co. and was told they could not open mp4 files I prepared in Apple Compressor. I took this preset "mpeg-4 300kbps" and modified it for 16x9 The client said they just got a question mark when they tried to open it. (extensio was .mp4)

I purchased a guide last year "SimpleEncodingRecipes" that said (paraphrasing) that using an iPhone video preset is the safest bet for a universal web video solution. Allowing for the fact that the client (PC) is downloading not streaming, I *do* want universal.

2 questions, first for corporate America, what is the best route for a Mac guy to prep such video files.* Second, if the iPhone flavor is viable, I can't seem to modify this preset for 16x9, others?

Thanks,

Paul

* I also have Flip4 Mac which can make (big & ugly) wmv files. Also have Cleaner 6 and Squeeze 5