1. Goto $ORACLE_HOME/Apache/Apache/bin and execute ./httpd -v or ./httpd -version.
In most of the environments you may not be succesful with the above command then you can use 2nd approach as given below.
INST_LOC is a regitry entry, which was used by the Installation:
If you dont find Components folder, then traverse to the folder Components21.
To know more about OHS, you can see the metalink note: 260449.1