To guide you on upgrading your own version, here is a step by step way of doing it.
NOTE: Make sure that you create a back-up first of you old Instant Rails version, just in case any problem occur during the installation.
Step 1 - Update your ruby version.
Download an exe installer at this link Ruby Installer for Windows.
Install it on
C:\Ruby193. Include the devkit and json files during the said installation.
When done, copy the content of your new ruby folder to the old ruby folder found inside Instant Rails, make sure that you overwrite all existing files.
Now start Instant Rails and type the following on your console to make sure that your version is 1.9.3
Step 2 - Update your gems
Now update your gems by typing on the console:
gem update --system
This action might take a while.
Now check your gem version by typing
Step 3 - Update your rails
Now update your rails gem by typing on the console:
gem install rails
This action might take a while. If an existing rails is already found, this will just overwrite and update the old one.
Now check your rails gem version by typing
By now, you should have a running Instant Rails version 3.2 that you can use for windows.
UPDATE: I forgot to mention that you need to use a different MySQL server now since the default one on InstantRails 2.0 is using 5.1.X wherein the rails 3.2.6 uses MySQL version 5.5