well guessing he has Windows XP im guessing Dx9.... uhh i've seen some videos on youtube of Crysis 2 and the guy had a GTS 250 aswell and was running it at high settings and 1280x1024 resolution so im guessing high but not Maxed...
i thing you will play it smoothly on high because i've seen that the recomended requirement of the game is
core 2 duo e6750 or amd athlon 64 x2 dual core 5800+
gts 240 or ati radeon hd 3870
2 gb ram
and you said that you play on 1360x768 or less resolution so i thing you can play on high