ppm install http://whatever/whatever.ppm > output.txt 2>&1 output.txt

That kind of redirection doesn't work in command.com, with which I'm (more) familiar. I don't have the slightest idea about cmd.exe, but if you're implying that it ought to work in it, then I'm glad to know that; OTOH I don't have the slightest idea about the WinCE environment, whatever it is, either...