I found it.
With my keyboard settings it's ctrl+K, ctrl +C (comment/uncomment), which is bit more logical than in visual studio when you have different shortcut for comment and different for uncomment. Only pity it's not obvious. As for this release of borland c++ first impression is very good unlike the previous versions when I switched them of after five minutes of playing with them and never switched them on again. Lots of cool, useful futures. I seriously think about moving from vs 2008 on to bc 2010. I wonder what your opinions are.