Windows Media Player 11 missing mpg codec

I'm using Windwos Vista Ultimate. I accidentally uninstalled Powerdvd from
the control panel yesterday, and my WMP 11 could not play mpg files any more,
and the DreamScene program also refused to work because of lacking of codec.
I went througth the online help and found that Powerdvd is integrated in
Windows Vista Home Premium and Ultimate as a support to some kinds of video
file formats. Since I have uninstalled it, how can I get it back? When I was
using Windows XP, I can simply unistall and reinstall WMP, which would fix
all the problem. How can I do it in Vista?
Any Help would be appreciated.

The MPEG codec WMP uses wouldn't be reinstalled that way, so that wouldn't
have helped here.

Under WMP's Help:About:Technical Support Information menu tool, what
DVD/MPEG filters does it list?