An .ISO file is a virtual copy of the physical CD that you can use with an ISO mounting program (e.g. Virtual Clone Drive, Alcohol 52%, Daemon Tools), and then install in the same way as if you had the physical CD yourself.
Once you have mounted the ISO to a virtual drive, you can the install to Windows. The WT CD cover lists requirements on the back as basically "Windows XP or higher".
An alternative - I think you could also use a program to extract the CD files from the .ISO image (as you may already have one - e.g. 7-zip or WinRAR) and install the program by running the "Setup.exe" installer.