If you receive error Exception from HRESULT 0x81070215 when you open a list or access the SharePoint site manager, a list has not properly been deleted and is in a corrupted state. You can change the corresponding custom list definition after you have deleted the list to fix the problem. Because the SharePoint pages don’t allow you to delete the list, you have to use the STSADM program’s forcedeletelist operation.
Although the help message displays information about using the forcedeleteweb operation, you have to use forcedeletelist instead. The syntax is:
stsadm.exe -o forcedeletelist -url <url>
See also the Microsoft Technet Library STSADM Forcedeletelist operation.