Scotia, GOOD FOR YOU! You are absolutely right. You don't have to do it perfectly or as many reps as they say on the video. Something is better than nothing. When I started this, I didn't worry about doing it perfectly or doing all the reps. I just did as many reps as I could (sometimes taking a rest if I needed it) and figured my muscles would improve over time. I still have to take an occasional break, but I can do all my reps, now, so I know I'm improving.
As Callan says, if you need to take a momentary breather, do it. I think the logic behind that statement is that many of us get discouraged when we can't do all the reps, and there is no reason why we should do something as well as someone who's been doing it for years. The way I look at things, that's one of the reasons a pause button exists.
I'm guessing that your PC is in the homework/TV room? Have you thought about buying a portable DVD player? You can download the video of your choosing (I've got a link somewhere; I'll find it if you need it. OR I can burn a DVD copy and just send it to you, if that'll be easier for you.), burn it to DVD and then you'll be free to do your workout where ever you find the room. Here's a small one for $40
http://www.consumerdepot.com/products.asp?id=E700PDD, but I've found that I don't need the video. I typed all the exercises out, with specific instructions, and I just use my paper most of the time. I've only recently been watching the videos on occasion before I work out to start correcting my form.
I've done Callanetics all over the house, depending on what's going on. I've used my kitchen counter or a bed rail as my barre, even my coffee table a few times. If you go with the portable DVD or take my (cheap) route and just write the exercises down, you can make it more easily fit into your schedule.
Zu, we won't kick your butt if you're resting when you need a break. Rest your body when it needs it. If you need to sit it out for more than just a day, by all means, do it. Heck, I took almost a week at the beginning of the month. You know how much rest you need. I don't.