when i press "rebuild all target" button in uvision3 then i get a error as follow ---ERROR: can't execute 'C:\Keil\C51\BIN\C51.EXE' Target not created pls help me.
"In the first place" is an English idiom meaning "originally" or "initially" etc
"i installed the software"
What software, exactly, did you install?
Did the installation complete successfully without errors or warnings?
Perhaps you installed some other toolset (eg, ARM, C166), but not C51?