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Answered by Sergei Chevtsov, 06-14-2007
Basically, use FileLocator .
http://help.eclipse.org/help32/index.jsp?topic=/org.eclipse.platform.doc.isv/reference/api/org/eclipse/core/runtime/FileLocator.html
Similar methods in other classes are deprecated and call FileLocator anyway.
To get a Bundle instance associated with the desired plugin, use ((Plugin)myPlugin).getBundle(). (http://help.eclipse.org/help32/index.jsp?topic=/org.eclipse.platform.doc.isv/reference/api/org/eclipse/core/runtime/Plugin.html)
If you can't access the instance of the desired Plugin, then (in addition to yelling at the plugin developer 
) use Platform.getBundle(symbolicName) where "symbolicName" is specified in the plugin's MANIFEST.MF file.
(http://help.eclipse.org/help32/index.jsp?topic=/org.eclipse.platform.doc.isv/reference/api/org/eclipse/core/runtime/Platform.html)
Finally, use new Path](myPath), where "myPath" is relative to the plugin's top directory, to get an instance of IPath. (http://help.eclipse.org/help32/index.jsp?topic=/org.eclipse.platform.doc.isv/reference/api/org/eclipse/core/runtime/Path.html)
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How can I manipulate the main workbench menu at runtime?
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Answered by Sergei Chevtsov, 07-25-2007
Use ErrorDialog like so, e.g.:
ErrorDialog.openError(shell, title, null, new Status(IStatus.ERROR, pluginId, IStatus.OK, localizedMessage, exception));
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