When you own a Digital Video Recorder or Media Center PC, there are times when you would like to watch the show you are recording. Do you have to wait for the recording to finish before you start watching it? In the days of VCR recording (not quite gone yet, but getting close), you recorded a TV show or movie, waited for it to finish recording, rewound the tape and watched the program. With a DVR or Media Center PC, you can start watching a show at the beginning while it continues to record, or even watch a TV program while it's recording! The difference between using a VCR vs. a DVR or PC is that the VCR is using tape to record, whereas the PC or DVR records to a hard drive, which can be randomly accessed while it continues the recording function.
Something I'll do a lot with my DVR is start watching a program that has already been recording for 15 or 20 minutes. The recording finishes before I get to the end, and I can skip through commercials. Pause, Rewind and Fast-Forward all work even when a show is recording simultaneously.
Having the ability to start watching a TV show or movie before it finishes recording, or while it's recording, is a terrific feature of Digital Video Recorders and Media Center PCs. It's just one more advantage that the new Digital Video Recording technology has over the days of VCR Recording.