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:
  [HKEY_CLASSES_ROOT\.txt]     "Default"="textfile"
  [HKEY_CLASSES_ROOT\textfile]     "DefaultIcon"="\Windows\iexplore.exe,0"   [HKEY_CLASSES_ROOT\textfile\shell\open\command]     "Default"="iexplore.exe file:%1"
  [HKEY_CLASSES_ROOT\txtfile]     "DefaultIcon"="\Windows\iexplore.exe,1"   [HKEY_CLASSES_ROOT\txtfile\shell\open\command]     "Default"="iexplore.exe %1"
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.