LG GSA-H2N burning slow down

Hi everyone, it’s my first thread here and i’m lookin for any help on this strange problem of mine…
the thing is that i have a Core2duo 6320 with 2GB ram desktop pc and when i try to burn any dvd disc in my LG GSA-H2N recorder and for that i usually use nero micro 8.0.3 or Ashampoo Burning Studio, but my problem is that if i let the burning process go all the way to the end without doing anything on pc (for example, go to my hard drives , navigate on web,etc,etc…) the burning speed increases till the maximum of the dvds i use(16x), but if i just simply open a explorer window or take some action on pc the speed will slow down but normally finishes the burning successfully…
Any ideas about this strange behaviour?
Thank in advance;)