Trying to understand how the AjaxUploader decides how to render the upload controls.

On my PC (IE ver. 7.0) when I access the AjaxUploader it gets rendered using the NON Flash version.

When 2 of my co-workders (they are using IE ver 7.0 as well), it gets rendered using the Flash version. Why??

 

What determines hoe the controls get rendered? Is their a document that explains all the conditions it looks at to determine how it will render the Uploader controls?