Well, I'm currently running two PCs as DVRs. They both run Windows Media Center, one has a ceton tuner card with a cable card in it, so I can get encrypted movie channels and such. I have a couple of silicondust network tuners that just get clearQAM stations off of the cable line. I used to have a couple of hauppauge cards to get clearQAM signals, but I wanted to get something external to give the video cards in that machine a little more room to breathe. I'm planning on moving the silicondust tuners to a tv antenna I installed at my new place, but haven't gotten round to wiring it up yet.
In terms of software, WMC is the most compatible with cable tv systems, and it comes free with windows (although it won't come free in Windows 8..). The hauppague tuners usually come with some simple dvr software, it might be good enough for you if you're just archiving stuff. There's also some free software called MediaPortal that is free and built into xmbc, I think. For linux, the standard answer is MythTV, but it's a pain to set it up, especially if you want to use a remote. Interestingly, MediaPortal just announced support for cable card tuners, and MythTV also offers support for some cable card tuners, although neither support encrypted channels like WMC.
I could never get my Hauppauge tuner to work with WMC or MediaPortal for capturing. I do use MediaPortal for playing media so it'd be great to get it to work. WMC would be ok too if it works in the background.
But the big question for your case is, what are they using up in Canada? I have no idea what broadcast or cable standards you use up there, so that's a big question mark. But if you can give me any more information, I can probably help you narrow things down.
I've been on basic analog cable for 20 years and have no idea about how the digital stuff works. I plug the coaxial cable into my TV tuner and it records what I want. That's all I know lol. My impression is that any upgrade for me will involve using a proprietary digital cable box from the provider ( shaw.ca/television/packages/ ), so in order to record I'd program an IR blaster (I think that's what it's called) to control the cable box and record the video from the box. I assume subtitles would not be available in the video stream. That's the extent of my impression, and I have no experience with it all... which is why I have been staying with convenient, ugly TV for so long.
If you can provide some tips or suggestion that'd be great. Thanks!