Can any of these games be played on a windows 8 O/S system or must they be played only on XP/Vista? I am especially interested in the Fallout series. Kindly help if you can. Many Thanks.
Norman

I have not played the Fallout series however, I have win 8 (not win 8.1 I refuse to upgrade for various reasons) and I have no problems with any of my GOG games.

GOG is good about making sure their games work on the systems before they release them from everything I have read.

Fallout is not available here anymore, but you can see the supported OSes on each game's page.

Here is a list of all the GOG games that are officially supported on Windows 8 (more than 700 games):
http://www.an-ovel.com/cgi-bin/magog.cgi?ver=241&scp=gdspur&dsp=ipgfsorlcmba&ord=&flt=oan~w08~&htt=&myf=ThuAug70715152014_empty_JJgLqrWPGuS5q

The list includes a few games that have been removed from GOG's catalogue (identified by a red slashed circle above the game image), which sadly includes the Fallout games you mention.