Question : Linked Mailbox & User Mailbox?

A month ago I migrated an Exchange 2003 system to Exchange Server 2007, the migration has been sucessful.  The migration was in a single domain and single forest, and followed the extensive migration checklists provided by Microsoft.
 
All of the migrated mailboxes are a 'User Mailbox' and only one (1) user (General Manager) are a 'Linked Mailbox'.  At the time I did not take much notice of this but I have more recently become concerned that there could be some undesirable side effects.

I have several questions please:

1. Why have all mailboxes become a 'User mailbox' and only one 1 a 'Linked Mailbox'?

2. How do I avoid this happeneing again?

3. Are there any undesirable side effects or limitations of using 'Linked Mailboxes'?

4. How do I convert a 'Linked Mailbox' to a 'User Mailbox' without losing any configuration or affecting the users?
Please any Help???
Thank You...

Answer : Linked Mailbox & User Mailbox?

1. Open EMC
2. Select Recipient Configuration
3. Select the Linked mailbox and right click and disable (this will delete the mailbox)

Part 2
Open Exchange Management Shell (EMS)
type: get-mailboxdatabase | clean-mailboxdatabase (this runs the clean up agent)

Part 3:
Go back to EMC
Select Recipient Configuration
Select disconnected mailbox
Find the user mbx you deleted
Right click and connect