Running Gallery 3 on Windows environment is not officially supported by Gallery Team.
The following should not be taken as a promise that Gallery 3 will work on Windows.
These instructions are only based on users' experience and provided on voluntary basis.
These installation procedures have been carried out with the following software:
Installing these with default settings will do.
Create a database and a user for Gallery, grant the user rights for accessing and modifying the database.
Download Gallery 3 and place it in Apache-readable folder (eg htdocs). If you wish, you could create a separate virtual host for gallery (gallery.example.com) or an internal server alias which allows to install Gallery to a different folder or disk outside server location (for example Z:\gallery3).
Fire up the web browser and in case everything above was set up right Gallery should welcome you with the installation screen, asking for MySQL credentials.
Correcting the admin dashboard platform information block: Gallery3:Modules:win_platform
Please, feel free to point me to some descriptions and I could try to explain how solve the problems.