Now available in digital format for the first time at a cost of $9.99 (~£6.50 using today's exchange rate) after years of legal wrangling. This is the original version but optimised for resolutions up to at least 2560x1440 and Windows XP, Vista, 7 and 8 friendly. This will work on old PCs as well as new.
http://www.gog.com/gamecard/system_shock_2
http://www.gog.com/gamecard/system_shock_2