Version 87 can run on very low PC performance, but I guess minimum will be winXP.
Version 4 takes some more resources because off the advanced driver, also the GUI have some serius updates during the race. But we have tried it on Win7 and 8. I also have a pretty slow slot pc, I have had a lag feeling if I used Sorting dashboards when having 6 drivers. But after deaktivating this feature no problem at all.
Martin