Hmm...maybe you could try Freemake Video Converter. as title implies, it is free and convenient. I've been using it for quite some time and had no problems so far.
To convert: Add the desired video, then the 'editing' tab will appear together with the video. To the right you will see 'Add subtitles'. Search for desired .srt file or any other sub file format. After that just click Convert -> To AVI. Configuration pane will appear. Modify it to suit your will and wait for the conversion to end. That's pretty much it...
here's the link to the official site
Free Video Converter| MP4 FLV 3GP AVI MKV DVD| FREE Download