The original dos Sidekick--ahh, those were the days. Actually I had not played around with Sidekick until the Windows versions came out but I knew others who religiously relied on their dos version when it was around.
All of my important contact info is in my Sidekick 2.0 which I still use daily on my WinXP machine. The greatest attraction for me is the free-form cardlog field where I can make any notes and keep a running history of conversations, etc. I never was able to find as competent and simple a pim as Sidekick.
My only two wishes were that it would have been nice to have a nested structure to the card file (i.e., so that you can have just the company name appear and then the various contacts who work at that company versus having a bunch of cards for that one company, each with a contact) and I regret not being able to customize fonts or have occasional text that is bold or different size. But still I rely on Sidekick pretty heavily in spite of those minor shortcomings.
Doug