ok, The burning device (CDRW/DVDRW), is not limited by the computer unless the PC is unable to handle moving data into the the drives buffer. This is ussually the case when the Computer is running with too little ram or is just old. What happens is that the machine will need to use the data bandwidth that the CDrom is trying to use, and so the dive will slow down (burnproof) and cache data until it has enough to write.
so, for the most part, you will burn at the speed your drive can do, but there are times when that doesn't happen due to the above.
better?