I would get a cheapo TV tuner card for the PC and combine it with SnapStream (http://wwww.snapstream.com) which offers many of the benefits, as well as ease-of-use, as TiVo and ReplayTV but without the high cost of buying a device).

Alternatively, a number of PC manufacturers are making devices specifically supporting Microsoft's Windows XP Home Media Center edition. It's an elegant solution out of the box and the new version of the OS has, I hear, ironed out many of the earlier glitches. From memory, Sony is among the OEMs producing laptops supporting XP HMC.