If installing software onto a Windows CE device you see "XXX is not a valid Windows CE application" But you are sure it is, you can try compressing the exefile with UPX Shell.
Some Windows CE builds can't seem to run large exefiles, but compressing them seems to work.
Download [Please Register or Login to download file] and install.
Start UPX Shell.
Click Open file/Open.
Navigate to the exefile.
Click Compress.
Select UPX 2.92b from the drop down menu.
Click Go.