One thing you need to do is go to the following link and do everything listed. Then restart the computer before opening Hoster. XP did not require all these steps, but Vista and Windows 7 do require this.
http://www.mtu.com/upgrades/hoster/windows7-changes.htm
Version 3.316 was Vista compatible but I don't know for sure about Windows 7 since they made a lot of changes (Microsoft). So you may need to upgrade to 4.20.