1.Can i set default reading pane is bottom by registry?

No

2.Can i set?default "Message Fonts" by registry?

Yes. From my latest book:

Outlook's font settings are located in the HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\C ommon\MailSettings key, probably because this information is shared by Outlook and by Word, when Word is used as the email editor (a configuration known as WordMail). You can either export the MailSettings key from the registry of a machine configured the way you want it and then import that .reg file into the CIW or CMW, or you can use the Office Profile Wizard to capture these settings.

3.Can i set default custom menu bar by registry?

No.

--
Sue Mosher, Outlook MVP
Author of Configuring Microsoft Outlook 2003
http://www.turtleflock.com/olconfig/index.htm
and Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers
http://www.outlookcode.com/jumpstart.aspx