If you need to record a lot you will need a huge hard drive in any device that can do it.
250gb / 500gb / 750gb or even a SAN storage area network as this can hold plenty hard drives and connects to the pc's network cable / usb . 3TB or 3000gb or more but expensive.
1 hour hd = something like 4gb at 720x??? resl. not sure or 1 hour = 1 dvd not sure might be more.
Look for maybe a 16mb cache hd and 7200rpm min in SATA or SCSI for best playback or similar.

Windows or Linux. Windows = $$$ , Linux = No $$$ just time and reading a few pages.

If you go the computer route here is some links to linux mythtv but is not limited to linux only.

These 2 links make it look very difficult but pclinuxos = so easy like running a sat receiver box. Even my mother can use pclinuxos.com

Pc Hardware
Installing and using MythTV: Checking prerequisites.

General terms / wiki for DVB
Main Page - LinuxTVWiki

I just got a copy of pclinuxos.com and it has all / most of the software to do this and it is for free.
Similar is Videolinux.net also based on pclinux but also extremely easy to use and if other software is needed you can just download it or get it from mandriva.

If you just want to do a hardware / all in one box you are likely looking at about min. $399+ and only limited amount of space.

Viewsat pvr 7000 , Dreambox etc. google for "satellite pvr"

Some of the pc cards I have seen like wintv pvr has a s-video out and normal cable out but not HD

Most new video card for pc's has the DVI ?? out maybe this can help or have a connector from that to what can be used on your tv.
A nvidia 6800 gtx/ultra top of the range can drive 2 Apple 32" LCD's at 23??x16?? insane resolution.

Ati X850 goes for about $150 on ebay and is extremely good bang for the bucks , next up from that is the x1800 / x1900 or better.
XFX 6800 extreme in pci 16x or agp 2 HD out and about $123 + shipping

Nvidia any of the ?800 versions 6800 / 7800 / 8800 maybe gtx as this is default and all others gets build from this as their base and modified.

Estimated cost of new pc + needed hardware = about $ 500 and then pclinux = free or windows MCE = $120+ ? extra.

Hope this helps.