Um, Photoshop should be able to read and write GIFs, at least mine does If they're images you got off the net, it's possible they're partially downloaded or corrupted - IE would still show as much as possible but Photoshop would reject them completely.

There's always MSPaint (comes with Windows) or MS Photoshop (comes with MS Office '97 and later), you could use either to convert to bitmaps - photoshop shouldn't have any problem reading those then, unless something's wrong with Photoshop itself.