Nero 7 Ultra to run in background

I often convert video file formats and I'd like to know if it's possible to relegate this to a background proggie where it will only use as much CPU as is available or forced, like folding.

I have an AMD 64 Venice 3000+ and 1 GB RAM so my rig is no slouch. I've tried changing it in processes and it still pins my CPU and makes surfing etc. unbearably slow. There doesn't seem to be any options in Nero itself either.

Any help greatly appreciated!