why is spatial analyst greyed out

Discussion created by moumita on Apr 23, 2013
I am new in ArcGIS ,previously i was using MapInfo. I have a data of which i need to prepare a map with isopleth lines. so for this      when i'm clicking on the customize>toolbar>spatial analyst, spatial analyst become greyed out. i have turned on the spatial analyst    from the extension menu and made the raster layer turned on, but there is no result. I'm using the ArcGIS 10.1.

I will be really grateful if anyone could help me out.