Check w/your Telco & ISP. Some services are offered free of charge or are substantially reduced in price if you have existing service.
There are three types of ICID. 1. Software Only 2. ISP/Telco Hardware 3. Hybrid of #1 & 2
Nearly all of them offer a trial period (if $4 - 6 dollars a month is too much to spend, you shouldn't have a problem w/reinstalling the software once a month. Of course, you might have to learn about registry cleaning and file system maintenance).
Otherwise, unless you're using something like:
Call Wave & Pagoo (which you've already mentioned you don't need voicemail) you're kind of stuck on alternatives.
Looks like anything worth using, is worth paying for. I found a couple free, non-licensed beta ICID progs but I wouldn't try them (you don't know where they've been

). The sites were no longer maintained and the software never left Beta, but there's probably something out there that'll do what you're looking for - for free, I just don't know if I'd trust it. Caller ID only.
But,
GOOGLE is where everyone else is going to go looking to give you answers. It doesn't look like anyone else uses a COMPLETELY free ICID that isn't trial-ware or at least has seen your thread - so
BUMP.
BUMP,
BUMP away 'till someone does, or keep asking
Mr. Wizard the meaning of life...
-Sketch