The quality of the picture you can record on your PC will depend on your PC specs, unless you buy a TV card that has a bulit-in encoding chip.
To record at dvd quality you will need digital tv input and a processor higher than p4 1.8 Ghz or Athlon 2000+.
I have two pinnacle tv cards and record all my tv progs. on my pc's, it has made the vhs recorder obsolete :D