A new version of Codecs Package v1.28 for Windows Vista 64-bit Edition is available for download. The download package contains only codecs and filters that allows you to play audio and video in any multimedia player installed on Vista such as VLC, Windows Media Player 11 or Windows Media Center. You can also stream content from web browser once the codecs are installed properly.

Some of the codecs and filters available for Windows Vista x64 are:

QuickTime components
RealMedia components
AVI< ->AC3/DTS
CoreVorbis
DTS/AC3/DD+ Source
DirectShow and VFW ffdshow audio/Video Decoder
FLV Video Decoder
MPEG4/MP4
ShoutcastSource Filter
Ogg Vorbis
DivX
XviD MPEG-4

You may need to turn off UAC during the installation of the codecs package

Download Codecs for Windows Vista x64 here

Bonus Tip: To switch to x64 version of Windows Media Player, run the following command:

%windir%\system32\unregmp2.exe /SwapTo:64