I bought something like this a year ago for ripping all of my old analog stuff to hard drives.
It only cost me $20 at the time and you just connect the device (vcr, camcorder, etc..), press play, and then record it on your PC while it plays.
For watching or recording your cable TV all you need is to connect your cable box to your PC via Firewire. You can watch and record thru VLC and the video quality of the HD stuff is light years better than watching thru your cable box + you see the complete image. It's amazing how much of the picture is cut off when running thru a set top box. VLC can be a little glitchy when recording, but there's another program (forgot the name, but I have it at home) that records TS (Transport Stream) files perfectly. You then convert the TS files to x264 and you've got reasonable files sizes with 99.99% of the quality of the original.