where best to start?

[astralclouds]

I'm about to start on a project to create a state of the art HTPC to complement the rest of my home network. I read up on OS and PVR options and am interested in GB-PVR because of it's claims on extensibility and compatibility. I'm a professional software architect so this sounds like a good option for me.

I'd be interested to hear other's opinions on the following:

• operating system choice
  
• hardware 'must haves'
  
• ideal high level design for a networked HTPC
  

[-Oz-]

To answer these questions we'll need to know what sort of tuning source you'll be using. I'm not sure if the UK has HD but that will change the videocard your computer would need.

Also, will you be using this as a server where noise doesn't matter or right next to the TV where quiet is important (i went the quiet route).

[astralclouds]

UK has good Digital and Satellite choice. I'll mostly be tuned to Freeview plus possibly some HD satellite feeds in the future.

As I already have a hefty file server elsewhere on the network, I'm intending for this to be used mostly as a next-to-tv media centre but with enough local storage to handle recording needs (say up 1TB - I have 3TB elsewhere). One question that has come to mind already, is it feasible to use a liquid cooling system, such as the Gigabyte 3D Galaxy II, with a 170mm high media centre format? I'm very happy since I installed this on my server - no more dust and fluff and total silence (apart from PSU fan).

I've looked at Silverstone cases. One choice to make is ATX versus MicroATX. Another is the TV Tuner/capture hardware. Does 64-bit give any real advantage over 32 in media application?

So many questions....

[herbs]

I would avoid 64bit OS at the moment unless your tv cards have drivers for them.
I'm just outside London in the UK and have 4 tuners (3 dvb-t/freeview and 1 analogue for cable) all running on a duron 1.6Ghz with 1GB of ram, so you do not need anything too heavy to run gbpvr. If you are just going with dvb-t tuners I do not believe you need more than 3 or 4 tuners due to +1 channels and often repeats.
If you are looking to build a system I would look at a dual core cpu something like a E4400 or a amd x2 4400 with a good cooler, and either a geforce 8500 or ati 2600 for HDTV stuff.
I have an antec 2400 case that can hold 2 hard drives without issue, so you could easily go for 2 x 500GB hard drives with enough storage for plenty of recording.