I have the cron manager extra running on my windows 2008 box with IIS 7.5
Here is how I did it:
1. Install the package:
http://modx.com/extras/package/cronmanager
2. Create a batch file named modx_cron.bat and put this inside of it:
Note I placed my batch one folder up from the web root.
cd\
cd "C:\PATH-TO-PHP"
php C:\PATH-TO-YOUR-MODX-INSTALL\assets\components\cronmanager\cron.php
3. Now open up Task Scheduler and create a new task, see:
http://www.devx.com/DevX/Article/39900/1763/page/3 for more info. Set the trigger to repeat daily and under advanced settings click Repeat task every: and set it to 1 minute or what ever you feel comfortable doing.