Perhaps I shouldn't start guessing, but I'll do it anyway:

MarcHoeppner wrote:
- long start-up time of media player in general
- things in the background (like copying a large file) bring the OS to a halt, consequently ruining the 'multimedia' experience


These can most likely be attributed to both the OS and FS implementation etc. Forgetting network copying, I have found that having atleast two drives, so that you never do copying inside the same drive together with HT P4 makes a quite good combination. Problems usually arise when many applications access same drive almost simultaneously. For this reason my minimum recommended configuration for XP power user is 1 GB memory, HT P4 and 3 HDD's with such setup that you can allocate heavy tasks to occur in different drives at the same time.

MarcHoeppner wrote:

- codec hassles (there never seems to be the right codec on the machine you happen to use)


Lets see, maybe the video files could carry a source code for decoding the data and then the player would compile this if necessary before playing the file. LOL. Or perhaps MS doesn't want additional legal burdens associated with some codecs. Just guessing.