Those having a NVIDIA gfx card, either FX series or above, can simply try Purevideo decoder for DVD/WMV/H.264 playback
I use WMP10 with Purevideo decoder, Real alternative, cos i use it only at raaga.com
Quicktime is required, i so like the H.264 codec
For music, I use winamp, but if somehow I can manage to get Windows media player 10 to minimize to tray, i will switch instantly
in case U have nero installed, then u don't need any other Software DVD Player etc to play, it installed the required codecs automatically