Lots of free GIS software out there - find it with a simple google search; just have to be wary of what each does (many are simply components to 'build your own').
Have a look at these:
They increase in capability from top to bottom.
Arcexplorer-was built as a light weight viewer but they keep making it better and it can do more and more; Windows and Java-based programs.
fgis - is a good one also but has some 'quirks' that need workarounds (these are described in the online forum).
Best - Ilwis was built by The Netherlands based ITC (Institute for Aerospace Survey and Earth Sciences) as a full-fledged commercial GIS.
Full raster and image support (the program's original main focus).
However, they have made Ilwis FREE, completely downloadable and with full documentation and example datasets also downloadable. It also has available several language packages including Slovak, Spanish, Thai, etc.
Since this is a FULL PROGRAM, it may require a longer learning curve. Overall, if you have the time to invest in learning the program as well as using it, this is probably your best bet.