WMP 10 should install without removing WMP 9.
Evidently WMP 10 supposed to take 55 mins on a 28.8 modem.
I guess you never 'saved' the file but 'ran' it.
I would suggest downloading again and 'save' to My Documents for example.
At least you won't have to wait around to keep downloading it.
If you can open WMP 9 or 10, go to 'Help' - 'Check for Player Updates' and see what that does.
If it says it will update then 'save' as I mentioned earlier, before running it.