I installed a pure Drupal on Windows/IIS6 share host, and uploaded several modules in (sites/all/modules). When I want to enable some module together, my administrative pages become white, but front page and other pages work normally.
Take a look at The White Screen of Death (Completely Blank Page) to learn more about the WSOD and how to troubleshoot it.
I guess your
display_errors in php.ini is Off, enable it and you'll see your errors instead of white screen
Check if there is any space in the top of module file before
It's definitely not the best idea to work with Drupal on IIS in first place, however for situation with white screen you've described - I'd say it looks like it's not enough resources (RAM) dedicated to PHP / Drupal.
Solution for this either to increase RAM available for PHP / Drupal or, as option, enable modules via Drush, not admin interface. Thing is that Drush not working that well on Win / IIS platform.
Try checking the normal windows error log if IIS or PHP throw an error.