Over at Ars Technica, Adam Baratz does a fine job of reviewing five free Windows desktop search tools. Skip over the first few grafs of the long-winded introduction and you’ll get to this clear summary of the review criteria:
The real novelty of desktop search apps can be found in their interfaces. The central design problem in these programs isn’t finding the best way to catalog your information, but finding out how to let you best traverse it. A quick comparison of the programs reviewed here shows that there’s still a long way to go with this on interface design. There’s no consensus on a best method; everything from web interfaces to Start menu toolbars are used. However, this indicates that these developers are open to experimentation. The battles for the desktop has barely begun, but no one is going to let it go without a fight. Let’s see what they have to offer.
I was surprised by the conclusion (Baratz picks MSN Desktop Search as his favorite), but this review does what any good review should do: it gives you enough detailed information to help you decide which product is appropriate for you. Based on what I read here (and my hands-on tests of three of five products), I see no reason to change from my preferred utility, Copernic Desktop Search.
PS: Copernic Desktop Search just released a new version 1.5, with support for Firefox and Thunderbird, iTunes, network drives, and a host of other features.
(Via Marc Orchant)
Ed Bott 
I was also surprised by Baratz’s conclusion. From the article it seems MSN Desktop Search was his preference for now, and mine too. I’d choose Copernic for every feature except it doesn’t preview some well (not a big deal), and it doesn’t allow an option to selectively index folders and subfolders like MSN Desktop Search and Yahoo Desktop Search does. And since I have almost 400Gb of music and photos on my second HD, I don’t want or need them indexed! However, Copernic indexed my HD’s contents faster than any other search utility (a big deal).
Actually, Zaine, in Copernic you can specify which drives and folders you want indexed, and you can also specify what types of files to index in each location. Click Options, Files tab. Click the Add or Modify button to see your choices.
Thanks! I didn’t notice that from the 1.5 beta to the 1.5 final.