Well-one of my favorite subjects. On the standard PC side, using non-cable card computers and MCE, you can get tuner cards that will let you record OTA HD and NTSC SD. There's a relatively recent external product, "homerun", that will let you record whatever digital your cable provider provides "in the clear", via QAM, and within MCE.
If you have a cable card PC, you can record anything your cable provider has, provided you've signed-up for it. Cable card PCs must be delivered as such, and certified. You can't buy the tuner, and put it in a PC yourself.
Now, what you do with what you record, in both kinds of PCs, depends on the copy flags set by the program providers. If it's copy never-you can't copy at all. If it's copy once, you can record to your PC. You can't transfer the copy to another PC (electronically or physically) or DVD or whatever. If your PC dies, your copies go with it. If the flag is not copy limiting, you can make HiDef DVDs.
So the good old days of archiving our favorite movies are largely over, just when we can finally watch in HD.
Right now, on my cable, everything premium is flagged, copy once.
Yes, DVRs are still out there-but, again, you can't archive in HiDef, only SD.
Sitting there watching an HD movie in SD on your 65" HDTV can't be much fun.
I guess hard drive archives are OK, until the drive dies. By the way, if your DVR dies, can the drive be transferred to another DVR? I don't know the answer to this question.