Any TV programs that you record with Windows7 Media Center is written in a WTV format. Which is a new format for Windows7*. Which is fine if you only plan to watch it back on the same PC or on another Windows7 PC. If however you wish to watch it on a Vista or XP computer, or you wish to shrink the file size a little, then you will need to convert the file.
You can pay money for programs like WTV2AVI to do it but you can also do it for free in Windows 7.
If you right click on any WTV file, one of the options you get is “Convert to DVR-MS” file. Click on this and Windows will create a new copy of the file in DVR-MS format. This format can be read as is by Windows Media play on Windows Vista and Windows XP.
You can also do it from the command line using c:\windows\ehome\WTVConverter.exe
If you want to also save some disk space all you need to do is down load Windows Live Movie Maker and open the new DVR-MS file with that. WLMM allows you to do basic editing and then save the file in WMV format. That is the only format is can save the file in but it is still a good size reduction, and depending on the options you choose still good quality.
* – It is also used by some versions of Vista.