Go to Computer, and right click on your USB drive and click on 'Properties'. Once there go to the 'Security' tab (top of window). Below 'Permissions for authenticated users' there is an 'Advanced' button. Click on it. On the 'Owners' tab, there should be an 'Edit' button. Now, select your username in the bottom box, and make sure the checkbox at the bottom is checked. Click on okay, then once it has changed ownership, click on Ok on all 'Properties' windows. You should now have full control of your USB memory stick.