xbox 360. windows media center. SUBTITLES to work?

[UmmAddan]

i am a newbie to xbox 360.
recently i managed to 'connect' via router my laptop to my xbox 360.
on occassion it stops working but i somehow manage to get it on after fiddling with it for ages.
anyways i watch avi movies on my xbox 360 which are on my laptop (pardon the lack of technical language )
my question is how can i get the subtitles to work? most are in srt or sub or idx format.
on occasions (depending on my xbox's mood!) i view the movies via windows media center or "video player" option (again sorry if its the same thing).
thank you

[handyguy]

While it's playing press A and options show up at the bottom. I selected "Advanced controls" and then scrolled to "Subtitles" choices are:
"Subtitles off";
"1 English Subtitles" and
"2 Spanish Subtitles".

press A to choose.