Network Share Security

Goal:
Update an MS SQL 2005 database so that backups go to my new Windows 2008 Storage Server

Additional Goals:
Review the security of the backups and the services that run them.

Notes:
Initially, I just wanted to change my backup target. A relativley easy task, however when testing the SQL backup it failed every time - due to the Windows 2008 storage server not allowing access.
Although I want these folders to be secure, they were a little too secure.
On further investigation, I found that the service account for this SQL Agent had been left as Local Service. The Local Service account has a few too many privileges for my taste, so I created a specific service account for this DB, and changed the service. I also ensured that the new account (being a domain account) would have access to the share on the storage server.
The backups still failed.
After changing the share security to Authenticated Users, the backups worked flawlessly. Numerous checks and rechecks of the service account and the account the backup was running as, were all correct.
Next, (something i should have done previously) was enable auditing on the backup target share, and re-ran the backup.
Because I still had Authenticated Users setup, the backup worked, and in the Audit log i could see that the actual connection was comming from the computer account, not the user account. ( DOMAIN\SVR$ ). after adding this to the share security and removing the authenticated users group, the backup performed.
Hopefully that will help someone who may stumble over this post.