I have a Dell Dimension 9150...about 4-5 years old.  I am now getting at startup, the message "Windows could not start because the following file is missing or corrupt -  Windows\System32\Hal.dll, Please re-install a copy of the above file."  I have tried to follow the suggested fix by trying to boot from the Widows XP CD and going to the Recovery Console.  However, when I get to the prompt screen where you are supposed to enter "R" to get into the Recovery Console, the system does not respond to any keyboard entries.  I'm basically stuck there.  Any ideas or help would most appreciated.  Thanks.