Depending upon your Windows version, you will need to check the length of your default path. If your path is set in an autoexec.bat file, open the autoexec.bat file and make sure that the does not exceed 127 characters.
Otherwise, for example in XP, go to Start->Control Panel->System
Select the Advanced tab, then Environment Variables in the lower left of the screen (under startup and recovery). The Environment Variables screen has two sections, User variables and System Variables. Under System Variables, you should see a Path variable. You may need to scroll down to see it. Select Edit to check the path. For instance, mine is
C:oracleora92bin;C:Program FilesOraclejre1.3.1bin;C:Program FilesOraclejre1.1.8bin;%SystemRoot%system32;%SystemRoot%;%SystemRoot%system32WBEM.
This was first published in December 2003