I still use WMP6.4 and it works fine on sites like www.mp3.com for streaming music, its light and loads fast..
Some online sites bug you with a popup to try to get you to 'upgrade' to the nasty WMP9 but thats their problem. Don't do it!
WMP7 has the eye candy but doesn't load as quick as v6.4.
WMP8 is like 7 but more bloated.
WMP9 has the evil Digital Rights Management (DRM) spyware/software and once you install it you cannot remove it without a reformat.
The lesson is to do a backup before you install *anything* new from MS.
Check out www.xxcopy.com .