If you use the portable version of CDBurnerXP (occasionally updated and downloadable from http://cdburnerxp.se/downloads/portable/), you might get an error when adding files to the disc layout:
Unable to cast COM object of type 'NMSDVDXLIB DATAIMAGEXCLASS' to interface type "NMSDVDXLIB.IDATAIMAGEX'
CDBurnerXP requires a DLL, NMSDVDXU.dll, to be registered in order to work. When installing CDBurnerXP, this will happen automatically. The portable version however, can only try that on every start of the application. Registering the DLL may fail at that point and cause the error mentioned above. The solution is to register the file manually before starting CDBurnerXP.
To do that, open “Run” by using Start → Run or Windows+R on your keyboard. Type the following command and press OK.
regsvr32 "c:\program files\cdbxp\NMSDVDXU.dll"
Note that you have to replace c:\program files\cdbxp\ with the actual location of your portable CDBurnerXP version.
After that, you should get a positive message and the error should be fixed when using CDBurnerXP for the next time.