If you just need a text file viewer, you can open a file with Internet Explorer. Our current builds of CE allow you to double-tap a .txt file to do this.
If can't use a current build of CE, you should be able to add the following keys to your ADSLOAD.REG file:
Finally, there is a sample application in the HPC2000 SDK that might work for you. It's a Notepad lookalike called CEPad, but it is more for demonstration purposes than a functional text editor. On my system, the app installed to the following folder on my PC: C:\Program Files\Windows CE Tools\wce300\hpc2000\samples\evb\cepad\.
I expect one of these solutions will work well for your needs.