You might be stuck using your Cable companies brand of DVR if your Cable company encrypts its TV signal to prevent theft of TV signal, and you need a cable box from your cable company to view TV even on a HDTV. I heard Tivo was pretty easy to use, but it has a monthly subscription cost I heard.
I just use a computer to record my TV shows, but I still use analog TV, so the cable box does not apply to me. It is a lot cheaper. I use a Hauppauge 01200 WinTV-HVR-850 USB2.0 Hybrid Video Recorder 1200: http://www.amazon.com/gp/product/B00169CDUY?ie=UTF8&tag=johsgamsto-20&linkCode=xm2&camp=1789&creativeASIN=B00169CDUY , and so far it works great at recording TV shows to my computer to watch at a later time, and I only spent 50 bucks.
This link might help with watching Tivo recorded TV on a PC : http://www.tivo.com/mytivo/howto/record-once-watch-anywhere/howto_transfer_shows_pc.html
I think a Tivo is mostly for watching on your TV. But, if you own a digital video capture card/device : http://www.newegg.com/Product/Product.aspx?Item=N82E16815100033&cm_re=digital_video_capture_device-_-15-100-033-_-Product, you'll be able to record your Tivo's recorded shows on to a PC.