you should have no problems with your system spec burning a cd and doing other things at the same time.
im guessing here but try the following maybe:
have a good clean up and remove any programs you dont use to free up some disc space if you are running low on space on your hard drive then run a disk cleanup or something like this click here as it does a better job. then run a defrag and see what its like.
if you have plenty of space on your hard drive and have a good maintenance routine then maybe check your system for spyware using adaware and spybot and delete anything they find click here click here update them before running.
also make sure windows is up to date click here and maybe check DMA is enabled for your primary and secondary IDE channels in device manager. try updating your motherboard chipset drivers too.
update nero click here