I have set up an older laptop like this on my treadmill. I don't do actual "work" on it, but I can easily spend an hour and a half on it reading emails, looking at my friends' photos on Facebook, and catching up on the blogs and sites on my RSS reader.

Don't think "I wouldn't want to work that way". Think "How can I get off the computer and off my ass, which is becoming larger by the day." Instead think: "There must be some way I can make walking on the treadmill enticing."

I dislike exercising outside (I live in a huge city with limited green space and horrible pollution), I dislike going all the way to a gym (takes more time and costs a lot, and I dislike crowded, noisy spaces), so the treadmill has always been attractive to me. Only my treadmill had hardly been used in the first year and a half I had it by anyone but my cat (she loves walking on it). Then I read about people setting up computers with their machines. I took a simple shelf out of my home office and set it across the bars-- it is sturdy enough-- and placed my old laptop on it....I loved it!

I set it at speed 4, elevation 4. This keeps my heart within the specified "aerobic zone" yet allows me to type and read as I go. Sure, I can't type fast on it, but I can edit papers and write basic stuff. Recently I have started writing some fan fiction while I walk on my treadmill-- it is light and silly and gives me a real break from my day. I get so caught up in what I am doing that I can easily go for an hour and a half and not even be aware that I am working out. I sude to get so caught up in my work that I could not exercise, so this is a great compromise. Now I do my non-essential computer stuff while walking. Sweet.

I do not, however, do the "walk all day at a slow speed" thing. I have read that walking slowly at low elevation for hours is bad for treadmills, even when the silicon lubricant is liberally applied. They simply are not made for slow speeds. That's why I go for 4 x 4 and keep it to 60-90 minutes.

It's great. I look forward to my sessions, which have become like a guilty pleasure only there is nothing to feel guilty about since I am doing what my body needs most to lose my computer-butt. I feel I have finally set up an exercise system I will be able to stick with.