Marion,

As Malcolm's links show - the tuning of a sitar is fairly alien in terms of the western musical scale.

However, it has the huge advantage of having movable frets. If I was lucky enough to have a sitar sitting around the house, and wanted to play western tunes, I think that I'd 'cheat' and move the frets to western intervals (using a good electronic tuner if I couldn't do it by ear)

I'd then tune it in a 'western' style, tuning the sympathetic strings to tonics and dominants of whichever key the main strings felt most comfortable in.

This may well sound like sacrilege to purists, but it would be a lot easier to play western songs with the sitar sound.

Ed