Doing 2010 SP 3.0, at the Summary Page, selecting Download & Install, getting this message;

The installed Toolbox folder cannot be found: G:\Solidworks\Tool Box.

Make sure you have access to this directory.

SolidWorks installation or upgrade will fail if Toolbox is not present in this folder.

To resolve this issue, repair the existing installation or select a different Toolbox option.

This condition must be resolved before you can continue.

This folder is there and Solidworks is pointing to it.