Often we will get question that have to deal with deleting system folders in Exchange 2007. When deleting an OAB public folder from Exchange Management console, you receive the following error: 0x80070005. This error means "Access Denied." You will still receive this error even if you use an account that has Exchange Organization administrator permissions.
Logging will also show the following:
Action 'Remove' could not be performed on object - ‘/o=Organization/cn=addrlists/cn=oabs/cn=OAB'.
Error: The folder '\NON_IPM_SUBTREE\OFFLINE ADDRESS BOOK\ /o=Organization/cn=addrlists/cn=oabs/cn=OAB' or some of its subfolder(s) encountered errors and could not be deleted. MapiExceptionPartialCompletion: Unable to delete folder. (hr=0x40680, ec=0)
Lid: 18969 EcDoRpcExt2 called [length=54]
Lid: 27161 EcDoRpcExt2 returned [ec=0x0][length=85][latency=0]
Lid: 23226 --- ROP Parse Start ---
Lid: 27962 ROP: ropDeleteFolder 
Lid: 17082 ROP Error: 0x80070005
Lid: 21921 StoreEc: 0x80070005
Lid: 27962 ROP: ropNone 
Lid: 21817 ROP Failure: 0x80070005
Lid: 20625 StoreEc: 0x80070005
This is by design. You cannot manually create or manually delete an OAB root folder. These system folders are handled by the information store. When you create an OAB object in the directory via powershell or the Exchange Management Console, the owning information store will create the OAB root folder when site folder maintenance is run. When you delete an OAB object from the active directory, the information store will mark the OAB folder as unused during site folder maintenance. If it goes unused for 7 days, it is deleted by the store during site folder maintenance.