hi..
i got a logitech scroll mouse.but i am not able to able to scroll
though i have selected a scroll mouse during installation.

Open up your X configuration file with your favorite editor as root and look for the mouse settings. They should be in a section called Input. Listed in that section should be options like "Emulate3Buttons" "True", etc. Make sure, that in that section, the "Protocol" is set to "ImPS/2" and you have Option "ZAxisMapping" "4 5". Look at the other examples in that section to get the exact syntax. After that, save the file, and restart X. This should have been done automatically on install when you selected scroll mouse. However, nothing is perfect.