Question:
Does My Movies support subtitle files such as .SRT, .SUB and similar formats?
Answer:
My Movies for Windows Media Center passes the playback of your titles directly to Windows Media Center and the Windows Media Center SDK, which means that a question such as this actually refers to Windows Media Center in general, and not My Movies as such.
Windows Media Center requires a codec to support subtitle files. It is recommended that you install DirectVobSub (previously known as VSFilter), which is a DirectShow filter that hooks into the playback path, and allow both Windows Media Player and Windows Media Center to display subtitles.