i'm using a rather antique system (pvr only). but sometimes while watching a movie and i find myself wondering 'i _know_ this actor from somwhere...' i fire up a browser (with a wireless keyboard normally hidden in a drawer) and go to imdb.com
i did this once while i was watching something and recording two other things at the same time.
live tv began to stutter a bit (while the browser was started), but the recordings did not suffer any 'damage' at all.
so you most certainly will not experience any trouble.
AMD 1600mHz, 512 M RAM, 20+160 GB drive, Hauppauge PVR-350 + PVR-150 + PVR-150MCE, Win XP Pro SP3, using software decoding.
There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable.
There is another theory which states that this has already happened.
(The Restaurant at the End of the Universe)