You don't give enough information to give an exact answer but here are some general suggestions.
For the Mac, the current best DVR application is Elgato's EyeTV. This software supports a wide range of TV tuners for the Mac which covers, analogue, ATSC, US Cable TV, DVB-T, DVB-C, and DVB-S. In fact the only TV standard it currently does not support is DVB-S2.
For the US market, it does provide access to a free EPG (TV listings), for DVB-T it can access the 'over the air' listings. Otherwise you might have to subscribe to TVTV (it includes a years subscription). Annoyingly, they still don't support using XMLTV for listings.
The hardware you need will depend on the TV system you want to use which you did not state so I cannot answer.
An Intel Mac mini even with its built-in Intel video chip is perfectly capable of driving a TV display.
Elgato's website is at
http://www.elgato.com
The Elgato software will let you easily send a recording to Roxio's Toast to burn to a DVD.
Now, as I said the above is the current best Mac OS X solution, there is also the Tube from MediaCentral but it supports far fewer types of TV tuner, there is also SageTV which in my opinion is a complete joke as it supports exactly
two models of tuner (both analogue I believe).
I personally, even though I also have Elgato's EyeTV software, currently run (gasp!) Microsoft Media Center 2005 on my Mac mini. This is one of the few (possibly only) categories in which Microsoft have genuinely provided the best product on their own merits, without copying, stealing, or otherwise cheating, (which does not mean it is perfect). Media Center supports all the TV system listed for Elgato EyeTV, but unlike EyeTV it does not support subtitles for DVB-T, DVB-C, or DVB-S. As long as the TV programme is not marked as protected you can using various tools to edit, convert, and burn to DVD recordings. Media Center includes a free EPG service.
I have not bothered to upgrade to Vista Media Center since it adds, zero, diddly squat, zilch, not a sausage in terms of additional Media Center features for Europe (over MCE 2005). However if you are starting from new you may as well get the Vista version included in Vista Home Premium or Ultimate.
Of course we all wish Apple would come out with a version of FrontRow that also acted as a DVR. 😟