Here's what's driving me crazy at the moment

I'm looking into buying a DVD-Recorder. What I'd really like is a machine that can record onto a hard drive or a DVD, but they're really expensive. Added to that two things:

1. I'm supposed to be a poor college student and probably shouldn't spend that much money on anything to do with television.

2. I don't have a cable box. My cable goes straight from the wall into my TV, so if I want to record a television show when I'm not home, the DVR can't just talk to the cable box and ask it to switch to the appropriate channel. (Also, I'm really not getting Tivo, because while $300-$350 for the machine seems expensive but do-able, adding a monthly service fee is too much.)

Let's lay aside item one for now. Item 2: I can get a DVDR/HDD combo with it's own episode programming guide, but the ones that do have programming guides seem to be riddled with so many other problems they're really not worth the asking price.

Surpise option 3 is that I can buy a DVD-R that only records to disks. Here's what I want to know. Assuming that I am using some kind of RW disk, can I record a TV show one week, and come back later and record another show to the same disk without erasing the first show? Seriously, anyone?

While we're on the subject, I would like to take this moment to recommend the reviews on CNet. They've been most informative in telling me what features I will and won't need on a machine, most of which I hadn't even thought of.