Hi sribharath,
Check to see if you have the correct cui file loaded. Type MENULOAD and hit enter. You should have the ACAD cui file loaded. If not, click BROWSE and select the ACAD cui file, click ok, then click load.

If when you browse you don't see the cui files, the file location can be found in
C:\Documents and Settings\Administrator\Application Data\Autodesk\ACD-A 2008(This will be whatever version that you are using 2004,2005,2006 etc.)\enu\Support

Hope that helps,
nameci

you could try to uninstall Autocad, delete everything from Docs&Settings\"user name"\application data\Autodesk\Autocad\*.*
Install it again. It should work as all the files will be the new ones from your CD ...