The joys of dabbling with unsupported/unproven mods I'm afraid.
It sounds like that Spitfire either altered or deleted what was needed by the bootsector part of your installation.
The links below (especially the second one) should help you if trying to load from a previous save doesn't work.
Good luck matey
http://www.processlibrary.com/direct.../kernel/21533/
http://pcsupport.about.com/od/findby...sing-error.htm