Try doing the following steps from this link:
http://www.mtu.com/upgrades/hoster/windows7-changes.htm
These steps are for Hoster but Microstudio uses a lot of the same code used in Hoster. Also Windows 7 and previously Vista tries to control what you can use on the computer and these steps will help overcome that.
Before you try to open it the next time plug in the external drive so Microstudio can go through the set-up for that CD drive. This could be part of why it won't open.