525 and 528 come with openbox as the default window manager, do you prefer the jwm . well you are in luck here is all you need to get it back.
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- First when you have booted puppy press the keys alt+ctrl+backspace
type xwin jwm at the prompt. (that will boot you back into jwm)
open /etc/windowmanager delete everythign and type jwm then save the file. (if there is a file windowmanager.openbox delete it)
now you should have a fully functional jwm manager again