Well fooey - I have a few odd freebie image twiddling tools and/or links too them , but at work (and I'm not there now).
Try this:
Open folder containing your picture (.bmp).
Double-click on the file - should open in "Windows Picture and Fax Viewer".
Down on the toolbar (bottom frame), click on the little paintbrush lookin icon (should be just to the right if the little diskette icon). That will open the image file for editing (in paint, if you haven't installed some other editor, like MS PhotoEditor, etc.).
Once open in paint, you can save it in jpeg form.
Do beware of paint for general purposes though - it is generally a pretty k-mart kinda tool...