What percentage of personal computers can currently access the
following media players? (i.e. what is the market penetration of
each?) Looking for data less than one year old please.

Windows Media Player
Quicktime
RealPlayer
Flash
DivX

We are a software company and we are doing streaming video
projects.Windows Media Player & Quicktime are the most used in the
market from the list you mention. You forgat to add Java streaming
used all most in adult market.
Flash is the latest technology from Macromedia and is coming very fast
in front since has Microsoft support. The feature is Macromedia. Divx
is used like encoder and not working very well with flash for flash is
used sorenson codec from www.sorenson.com