I agree with you. AMD is pretty much faster than intel processors. I myslef has tested both of them. right now I have AMD athlon 64bit processor. and it runs...
It seems u don't have the proper rights to perform the operation. Start the SQL server Service (on server A)with an account which has the rights to access...
Before attempting to restore a backup, Verify the database for integrity DBCC commands & using Restore Command. See SQL server Help for further assistance