Here is my little penny's worth....
Ok,
If you have an AC3 file you can decode it into WAV using
Sonic Foundry's Soft Encoder
It should provide you with 6 channels of raw PCM
Convert these data to PCM WAV in appropriate sampling using
CoolEdit 2000
These channels can then be fed into
SurCode CD or DVD DTS encoder
which will then encode those channels to a Dolby Digital WAV (DTS)
This can then be burnt to CD/DVD, and you'll have a DTS audio!
Anyway, this is where you find:
sonic foundry soft encode 1.0
www.dvdsoft.net
Surcode CD Pro
www.shooter.com.cn:81/software/SurCode.CD.Pro.DTS.Encoder.v1.020-ZONE.rar
CoolEdit 2000 2.0
www.cdrsoft.cc