Windows Media Player Cannot Play Files

Clarifications

Maybe your previous installation had extra codecs installed?
Have you checked file associations for media player?
You say it cannot play media files. What are their extensions, what errors are you getting?

After completing the re-install of Windows you should have installed a set of 'device drivers' for your system's devices. This would include whichever sound chip is fitted to your machine.

If you are having difficulty playing video files, you need to install a CODEC pack. You can find many links to CODEC packs on the internet.

You'll need to go back to Windows Update and apply the rest of the patches, including optional upgrades to the media player, to bring it back up to the level it was before formatting. Applying SP2 isn't enough. There are about 74 OTHER critical patches that need to be applied, rebooting between patches, then applying more, until you get them all done. Once the critical patches have been applied, look in the optional ones for a newer version of the player.