Thanks for your reply Jay.
I have taken some time to work and unravel the possible reasons for why your Sony DCR-HC20 is not working with your Macbook 2.1 Ghz portable. Sony DCR-HC20 NTSC
As it turns out, your Macbook with Mac OS X 10.5.2 Leopard system, nor iMovie '08 or '09 whichever application you have, does not support this camcorder unfortunately.
Below I have even provided the links of the only available Camcorder compatibility lists from Apple for both versions of iMovie for your review.
I checked both lists over several times each and did not see your camcorder supported. This means that there will be questionable if not, simply no function as you noticed with your camcorder in interacting with your Macbook, with 10.5.2 Leopard and iMovie. iMovie '08 Camcorder Support
(Apple camcorder compatibility list)iMovie '09 Camcorder Support
(Apple camcorder compatibility list)
So to answer your question, this is the primary reason why your Macbook with Leopard 10.5.2 is not working with your model of Sony Camcorder.
If you have more questions regarding this issue, please feel free to reply back this post. I am always glad to assist. Thanks!