I think .CHM format stands for compiled HTML and it's what they make help files from nowadays. Anyway, the only thing I found for WinCE was that you'd have to decompile the file to view it. Not exactly the most elegant solution:
HTML Help vs. WinCE HTML-based Help
January 7, 2000
A question asked on occasion is whether or not HTML Help files can be viewed on Windows CE. Here's the scoop:
The minimum requirements for the viewing of HTML Help (*.chm) files is Internet Explorer 3 or higher (IE4 is better) and that the HTML Help viewer files are also installed by running hhupd.exe on the target machine. Unfortunately, this combination isn't installable on WinCE.
Help for Windows CE consists of Peghelp.exe and an HTML rendering application that enables a user to display HTML-based Help files. The HTML files for Peghelp.exe have the suffix .htp, but they're the same as files having a suffix .htm or .html, just with a different suffix.
There's a solution to be had, though. Both the HTML Help Workshop and HTML Help system architect Ralph Walden's KeyTools are able to decompile HTML Help files, as are some commercial help authoring tools, such as RoboHelp. This restores the raw HTML, contents (*.hhc) and index (*.hhk) files. Using these items, you can create HTML-based help for WinCE using the articles that start here (click Show TOC at the top of the page, and then Sync TOC to see the articles in that section). You can also use some of the commercial apps, such as ForeHelp, to put together the WinCE help from the raw HTML files.