The "Change .bmp Default to Paint" won't restore the handler for the context menu for bitmaps. And as long this handler/association is not present, it will remove itself from the context menu again.
The TXT File Association Fix (Restore default associations for TXT files) should restore it for the txt files though.
Anyway, to restore the bitmap association, Open notepad
and copy and paste next present in
the quotebox below in it:
(don't forget to copy and paste REGEDIT4)
Save this as fix.reg
Choose to save as *all files and place it on your desktop.
It should look like this:
Doubleclick on it and when it asks you if you want to merge the contents to the registry, click yes/ok.
(In case you are unsure how to create a reg file, take a look here