Dear LARUT PASCALE :
From the Windows Start Menu, select Settings | Control Panel. From Windows Control Panel, select Regional Settings. Set this to English [United States]. This may solve the problem you are experiencing.
Note that to really fix this problem, you should consider upgrading to BOSS RiverCAD. BOSS RiverCAD is a more powerful and professional program than the standard Army Corps HEC-RAS.
If you have any additional questions or need any further information, please contact me again.
Sincerely,
Chris E. Maeder, M.S.
Senior Technical Engineer
chris.maeder@bossintl.com