Thanks to asm495 and xs4all for their impressive and hard work we finally have H.264 decoding in VMC.
Download mirrors (x86):
MSDTVVDEC | RapidShare
MSDTVVDEC | Finland (Direct download, no ads)
Instructions:
1. Take ownership of the file (File -> Properties -> Security -> Advanced -> Owner -> Edit then select yourself.
2. Give yourself full control over the file (File -> Properties -> Security -> Edit then select Users and check the box for Full Control.
3. Run Command Prompt as administrator. Then type "regsvr32 -u msdtvvdec.dll" and hit Enter.
4. Rename MSDTVVDEC.DLL to MSDTVVDEC.DLL.BAK
5. Copy Beta DLL to the system32 folder and type "regsvr32 msdtvvdec.dll" in Command Prompt and hit Enter.

55" Sony Bravia FullHD | Yamaha RX-V659 | Yamaha Soavo 5.1 Surround System | Vista Media Center