I had these cases several times when installing SPs on somebody else's servers. This somebody has a preference to have different permissions to admins account to different drives. For example, SQL Server startup account has rights to the Data drive. The account that is installing an SP does have rights to the system drive (can start the installation, was authenticated OK at the beginning of the installation) but does not have rights to the drive or folder with database files.  Now this person makes sure the accounts that we are going to use have full rights and permissions on all drives and folders.