My WD HD Media Player supports only SRTs. How to convert subtitles from IDX/SUB to SRT?
here's a link at AfterDawn.com link text
although as NiklasS says, you'll probably have more success getting an SRT file from one of the subtitle sites. Converting can cause all sorts of issues with syncing the sound correctly, so it will save you more time getting the correct SRT file forthe film you've gotten hold of.