Just adding to the second response. In the US - Cable comes in NTSC (analog - Cable) and Clear QAM (ATSC - Cable). So if you have a hybrid tuner and your cable company (most are) is still broadcasting some analog channels then it should find all of those available (no locks).
But on the digital side it's a completely different story. Some cable companies is some networks / areas etc have all there QAM - Locked or " encrypted".
Despite what some will tell you they (cable comanies) are not required by the FCC to broadcast locals in Clear QAM (un-encrypted) ==> If they are supplying the locals already in Analog as long as they supply the locals in analog they need not supply them in Clear QAM. Many do (mine included) so when I scan the Clear QAM channels most of them are locked / encrypted, but I get 40 digital music stations that are Clear QAM 64, and then about 40 more digital (SD & HD) Clear QAM 256 channels (locals in HD & SD digital ) and then bunch of crappy infomercials in digital GRRR! Those digital channels that are unlocked are your Clear QAM. From time to time they may re-map or add remove channels so it's good to re-scan every month or so.
The only way for you to receive those (truly locked/encrypted - not just the ones that TM3.5 goofs up on) via the computer is to buy a Cable Card system. The cable cards are usually much cheaper to rent but the adapter that you install in the computer are expensive right now ... more are expected in 2010 and are not tied to certain manufactured computers they will work with a computer that meets specs to run them. Though some are many months behind there initial announced release dates.
Edited by DA1745 - 30 Jul 2010 at 7:54am