Audio type conversions

Is there any free software available with which I can easily convert my stereo recordings (two tracks) directly into Dolby 5.1 or DTS (6 tracks)? I am converting my old records (stereo or two mono tracks) to CD’s, but the stereo sound is a bit “thin” with only the two main (front left and right) speakers producing sound, and no sound at all from the sub-woofer in particular, and centre speaker or rear pair of speakers. My amp can use Dolby 5.1 and DTS to create 7.1 and DTS HD, but cannot play stereo recordings in a manner that will also produce sound for the remaining 4 (5.1format) or 6 (7.1 format) speakers.

Ideally, I would like to convert my stereo recordings straight into DTS HD, but will be very happy just to be able to hear it in standard Dolby 5.1 format!

Thanks,

Audacity can export multi-channel sound files, but since you are working from a stereo file you will need to think about how you want to simulate 5.1
The formats you have asked about are proprietary formats, so the is likely to be some kind of license fee involved in using those formats, however, if you can work out which channel corresponds to which speaker, you could put the bass on the sub channel and copy the front pair with a bit of delay or reverb for the surround,