Copy the ext-3.3.0 folder to the folder your isapi module resides. (don't rename the folder)
In ServerModule set the ExtRoot parameter to ext-x.y.z\ (You can select it from drop down)
If you copy Ext JS files to another folder, say c:\extjs\ext-3.3.0\ then ExtRoot should be either c:\extjs\ext-x.y.z\ or c:\extjs\ext-3.3.0\
If you copy Ext JS files to a renamed folder, say c:\extjs\ext3\ then ExtRoot should be exactly same value as full path: c:\extjs\ext3\
It should be enough to make it work.