Nero (media burning application for Windows) can apparently convert DMG files to ISO or CDR files, so that's one way around it -- although I wouldn't trust any kind of conversion process in this situation. I don't think it handles .TOAST files.
Veljo is correct in stating that .DMG and .TOAST are specific to the Macintosh platform, and your best results would come from burning those files on an actual Macintosh computer.
One option is to simply burn the .DMG or .TOAST file itself to a CD-R, then take that CD-R to a Macintosh, copy the .DMG or .TOAST file off of the CD-R, then re-burn it as an actual data CD using Disk Utility or Toast on the Mac.
If you can network the PC and the Mac, then you can convert the .DMG file to a standard .ISO file using the Macintosh, copy the resulting .ISO file back to the PC, then burn the .ISO file on the PC: