Only default file extensions work, bmp, jpg, gif, none work.

Hi, i have downloaded several versions of gimp they all work but one thing, they don't use any other file extension, i recently used system restore and thats when this happened. for example "Opening 'C:\Documents and Settings\Brian Truelove\My Documents\iNTERACTIVE HEAD\human_need_test.bmp' failed:

Unknown file type" i get that for a .bmp, i have no idea what the problem is but i could use some help.