If your pocket pc is running fine, then the OS is installed and running well too.
If your pocket pc is running WM2003, One Note Mobile will not be installed or run on the pocket pc.
One Note Mobile only works on WM5.0 pocket pcs. I had read this months ago, and just spent a few minutes searching through the web for confirmation of this. I also tried to install One Note Mobile on my WM2003SE IPAQ and it would not install (I do have it installed on my WM5.0 hw6925).
When searching the internet just now, I came across a
OneNote Mobile Patcher that allows you to install and run the application on Windows Mobile 2003/2003SE devices. I haven't tried it out myself, but you might want to give it a go.