[...]I have also tested CDRWIN in the past, and it wouldn't work either.[...]
HOW TO CREATE A MULTI-SESSION AUDIO CD WITH BURNATONCE:1. Burn the audio CD portion:Click 'Settings > Device Settings'. Now tick 'MultiSession' in the DeviceSettings window. Now add your audio CD as per normal by clicking'Mastering > Audio CD'. Click Compile when you're finished addingaudio files. When the audio CD portion is complete the disc will eject.2. Close Burnatonce. Start Burnatonce. Re-load the disc if it's still ejected.Now click 'Settings > Device Settings'. Now un-tick 'MultiSession' in theDevice Settings window.3. Burn the data CD portion:Now add your data CD files as per normal by clicking 'Mastering > Data CD'.After adding your data CD files click 'ISO Settings' and tick 'Add new session'.You must now manually un-tick 'Import Session' otherwise it won't work!Click Compile when you're finished adding data files. When the data CDportion is complete the disc will be finalized, and eject.Note: 'Import Session' is not required and can't be used since it's onlyfor merging two data sessions.4. Finished, you've created a multi-session audio CD (a.k.a. CD EXTRAdisc). Test it on both your computer and audio CD player to make sure itworks.Tip:You can forgo allot of settings changes in Burnatonce by instead usingthe freeware Burrrn to make the audio CD portion. In Burrrn just un-tick CloseCD then you can simply go directly to step #3 in the Burnatonce instructions towrite the data CD portion. This is the method I use and it's a tidbit quicker, andthere's less of a chance of forgetting to enable/disable settings in Burnatonce.Note:Not all burner drives support the creation of multi-session discs even thoughthey're advertised as supporting them. Such is the case with some Sony/NECOptiarc DVD burner drives. Also some drives won't be able to load the data CDportion of the disc.