Help! Reinstalled Windows XP. Can't re-install Hoster

[ddouglass]

Nothing you can do about it. When you re-install Windows it sets a new SID (System ID). Which means that Hoster thinks it is a new machine.
However MTU no longer provides support except by web-email ticket on their Support page. So if you didn't fill one out be sure and do that. Include the email address you ordered Hoster under, the reason you need your registration reset and the computer name it was installed on (if you were up-to-date enough to have added that).