Understandable concern and definitly would have been very real a few OSes back, but with proper CPU scheduling by the OS it works fine on 2K & XP - try it and see.

Maybe some one can correct me on my interpitation, but as I basiclly understand it ripping is not a heavy CPU user, but when it wants it it needs it now. Encoding is CPU intensive, it will take everything it can, but does not mind if it has to wait.
The way I think of it is that ripping is giving a higher priority then encoding.

I know on my P4 2.8 with a Plextor it encodes faster then it rips, but not much faster. On a previous PC the queue would grow quite long, at the end of a ripping session I would just leave it there to catch up and I haven't noticed and glitches or pops.