If the upgrade installation to WinCC version V7.0 SP2 fails, this may be because you omitted to uninstall the WinCC options before installing the upgrade. You can find the upgrade installation procedure on your DVD under "Install_and_Release-Notes > Language > InstallNotes.pdf". It states in point 2 of the section on "Procedure", section 7.3 of this document, that the WinCC options have to be uninstalled before an upgrade is installed.
If you have begun to install an upgrade, you have to perform a complete new installation even though a WinCC option, such as the Web Navigator, has been installed. You can find a description of this in the afore-mentioned document in section 5.3.
Upgrade, Update, Service pack