you’re at 3.5R2, so
[color=red]These following instructions only apply to people who have the original release ZBrush 3.5
Anyone who purchases ZBrush or redeems their upgrade link from this point forward will receive the new version automatically.
If your folder is already named ZBrush 3.5R2 then you have the most current version and do not need to install this update.
INSTALLATION INSTRUCTIONS…
If you currently have activated ZBrush 3.5 on your system, you may want to first deactivate it by using the Web Deactivation
button found in the Zplugins palette. When done, continue with the following steps…
Download ZBrush using the link that was sent to you AFTER you upgraded. This is in the same email that has your ZBrush 3.5 serial number.
Extract the Zip file and Move the ZBrush 3.5R2 to your preferred location. (Usually, the Program Files\Pixologic folder)
Open the ZBrush 3.5R2 folder and run ZBrush. (For Vista and Win 7 users, right-click on the ZBrush icon and select “Run as administrator”. )
When presented with the activation window, click on “Web Activation” in order to activate ZBrush immediately online. (For fastest completion of your activation, copy the key from the web page, return to ZBrush and click the “Enter Code” button. )
It’s all there (not meaning that you can’t discover your unique bugs) -
Good luck with it!