Designer 2007 Workflows

Folks,

I'm pretty new to Sharepoint.  At any rate, I have WSS 3.0 and Designer setup, and they appear to be working properly.  I cannot seem to get SP to start the workflows that have been done in Designer.  I can manually execute them, but they won't trigger automatically on my list or libraries.  I've checked the Administration Settings and my Permissions, all appears in order, per the books and help screens.  I've checked for corrupt XML forms, but all checks confirm a "healthy" file.

Any suggestions would be appreciated. 

Thanks!

Barry