When a TV show is recorded in Windows Media Center, it's saved as a Windows Recorded TV Show file with the file name extension .wtv, in the Public Recorded TV folder (usually found at C:\Users\Public). Older versions of Windows used a different file format for recorded TV with the .dvr-ms extension.
Files with the .wtv extension aren't supported in previous versions of Windows, as well as some third-party programs. However, you can convert your .wtv files to .dvr-ms files so that they'll play in programs that support the older format.
Go to the folder where your recorded TV files are stored (usually C:\Users\Public), right-click the file that you want to convert, and then click Convert to .dvr-ms Format.
The new file will be created and stored in the same folder with "DVRMS" appended to the file name.