Installing and upgrading help

First you need to decide on a few more things:

What web server do you want to use on that Windows server? IIS or Apache?

What database? MySQL, MariaDB, MSSQL, PostgreSQL...?

Then you should do some reading to get a background understanding of the Moodle installation process. Without that you'll struggle a bit...

Most importantly, start here:
http://docs.moodle.org/26/en/Installing_Moodle

Then read some of the more Windows specific docs, like:

http://docs.moodle.org/26/en/Windows_installation
http://docs.moodle.org/26/en/Manual_install_on_Windows_7_with_Apache_and_MySQL

If you want to try Moodle before you install it on that production box (e.g. on your own PC) you can start with:
http://docs.moodle.org/26/en/Complete_install_packages_for_Windows
http://download.moodle.org/windows/
But be aware that those aren't ideal packages to install Moodle on a real life production server. Those installers don't install Moodle in a way that can properly handle real-life production server student volumes...

The guys at BFC Networks have also published some nice Moodle installation whitepapers for Windows. See http://www.bfcnetworks.com/whitepapers/