Seriously long post coming up Gill
It depends on what your current pc is and where it is in relation to the TV Gill, also possibly what kind of TV you are using.
If you can put up with the abysmal picture quality of plasma and LCD TV when viewing an SD source then the connection to the pc should be very easy, either through DVI, VGA, HDMI or Component.
If you go for a CRT TV option so that you can get a good SD picture then the connectivity may have to be DVI, VGA or even S-Vid to a scart adaptor.
Some older CRT TVs had component inputs that would be a good way to connect.
If you had one of the Samsung Slimfit HD CRT TV like I have then thats the best way for SD TV and is great on HD, allowing the pc to connect via component or HDMI for both SD and HD viewing but you may struggle to get one at the moment
PC specifications would necessitate you having a reasonable good dual core CPU.
I wouldnt go below an Intel D800 series dual core and would preferably go for the new Core 2 Duo or even Quattro, I dont think any AMD CPUs are in the same class at the moment, unless you are spending serious amounts of cash and then for that amount of cash youd get a better Intel Quattro anyway.
I use an Intel D945 3.4ghz dual core CPU in mine, unfortunately I built it before the Core 2 Duos came out and the chipset wont run any faster than the D900 series.
Use as much ram as you can, at least 2 gig preferably 4 gig running in dual channel mode.
A good PCI express graphics card, I like the Nvidia 8000 series cards as they will do HD TV so you will be future proofed a little, if thats possible with pcs
You would need a big hard drive or preferably 2 or 3 as most TV recording uses around 2 gig per hour in the standard DVD quality, if you start getting HD recorded that will increase dramatically
For now a good multiformat dual layer DVD writer is ok, although some DVD writers with Blu Ray readers are coming out at more affordable prices now.
I wouldnt think it was worth getting a Blu ray writer yet as they are still very expensive.
Now we come to TV tuners.
I am not keen on USB for something like that and would prefer PCI cards.
There are plenty around now that seem to work well and do multiple tuning, some even do terrestrial, satellite and cable.
I currently only use terrestrial ones but am thinking of adding a DVBS 2 satellite card for HD satellite soon, maybe once the new BBC and ITV freesat gets setup this summer as that is supposedly going to have a few HD channels on it.
I use a Hauppauge Nova TD 500 DVB-T twin tuner in this pc which works great with windows media cente thats part of Vista Ultimate (I know you dislike Vista but its worth it for that feature if you want to use a pc for TV and DVD )
In my other pc, the one with the D945 CPU that I use for playing back on my TV, I have a Nebula master DVBT pci card with a slave USB DVBT tuner.
That allows me to record multiple channels at the same time as long as they are only on 2 diferent multiplexes for each tuner, from what I remember.
They are quite expensive but have excellent software that works with XP as well as the Hauppage does with media centre in Vista.
I hope I havent left anything out and have covered most of what you need to know.
If I havent answered properly for what you wanted then ask me again