Microsoft Office installs filters that enables MS Paint to handle new formats like JPG and GIF. One can use these filters separately without needing to install MS Office.
Download Graphics Filters (Download Mirror)
Note if using Windows 9x the registry file supplied with Graphics Filters will not work (Unicode). Instead use this MS Paint Codecs Fix to apply the registry settings.
Note if using Win95/WinNT4 one might need to update Mspaint.exe first. More Info MS KB162500.
More Info MS KB193354
More Info MS KB298580
More Info MS KB299953