<I have to format my computer installed with keil.What procedure I should follow to run the keil again after formatting my computer?>
1. turn on the computer 2. wait for the operating system to load 3. check what operating system is running 4. if it is Linux then try reformatting again 5. if it is osx then then try reformatting again 6. if it is MS-DOS then try reformatting again 7. when you are sure that it is running windows try logging on 8. if it is windows xp then seriously consider reformatting again with a supported version of windows
this is getting boring. have you ever installed any software on your computer before?
lets assume for a moment that you do know something about computers.
before you reformat, run up keil uvision and UNINSTALL the licence.
do whatever you have to do.
install uvision and INSTALL the freed licence from the above step.