Performance Alert - Automatically Start Job at Boot/Reboot

Last night our Exchange server stopped accepting new mails because of the disk space being completely used up. So to avoid this happening again, I created a performance alert which triggers when disk space is below 10%, and sends me an email with BLAT. All this is good, but the problem is if I reboot the server - the job doesnt start automatically. Is there any way to make the job do so, or am I maybe approaching this from the wrong direction and should try something else than a performance alert? Thanks a lot in advance.