Extensions Will Not "Hide" in OS 10.2.6

[Albert W D'Amanda]

Hello
Need some Help

When I open a Desktop Volume ( bootup 40GB Hard Drive) all the 
extensions are displayed

When I single click on and open  Finder Get Info, the Hide Extension 
check box is grayed out!( do not know why)

Is there some other way to hide extensions ?

Or have I corrupted my Finder Appl ?

Thanks to All that reply

Albert
B&W Yosemite  V1
  XLR8 G4 500 MHz/ 1MB Back Side Cache  ZIF Upgrade
1024 MB RAM
  OS 10.2.6