playing video on PCs

[sims]

I need to play video on both OS X and Windows machines which will
for the most part be business computers - corporate office machines.

The Mac part I can figure out and will be able to use QuickTime.

Some PC machines will not have QuickTime installed and will not want
to install QT. I need some advice on what format/codec to use for
these non-QT machines.

In the list archives I found this:

>Having said that, I suggest you save video in the best format/codec for
>each platform, and select the files on the fly according to the platform
>its running on.  For example, QT with Sorenson for MacOS, and .mpg with
>Indeo for WinOS.  I say Indeo as it's the only codec you can rely on being
>loaded on a WinOS machine.

Can anyone else give me some advise on:

1. what format/codec would be found on most PC machines - in other words
what is the safest way to go, would it be .mpg with Indeo as suggested above

2. what codec/format would provide the best viewing experience on PCs
which do not have QT - in other words what provides the best which can
be used via a Rev application

TIA
sims