Because Media Player doesn’t support all media types, you have to install a codec, sometimes more than just one. For Windows 7, I often use a codec pack from Shark007. When now they they have released a codec back for Windows 8!
If you need to upgrade from Windows XP to Windows 7 then you probably know there is no upgrade path - only a clean install. Have you thought about using the Windows Easy Transfer tool to help migrate your files and settings?
Having a Windows Home Server is a great way to store your videos, pictures and files so how do you manage the files between your PCs and the server? How do you synchronize files between multiple drives? Microsoft provided an answer. SyncToy 2.1