Thanks for the help, daffy4u. I followed the instructions and was able to try a book on 3 devices: Kindle 2i, Kindle4PC, and my Blackberry. The sync between K4PC and the Blackberry works fine, but I am unable to sync to the Kindle. I suspect it's my wireless connectivity. We had a hurricane in Oct/Nov last year, and the wireless on my Kindle has not worked the same since.
As I never use K4PC to read, this is kind of useless to me right now, but as soon as I get better connectivity and the Kindle sorts itself out, it'll be a great feature as my reading is spread between my Kindle and my Blackberry.
Thanks to all the wonderful people who put this together - you rock!
(Btw, thanks for realizing that I meant to say
Windows 7, and not Windows 6
)