Con(IsNull("myraster"),0,"myraster")
Try this:Con(IsNull("myraster"),0,"myraster")
This works in the Raster Calculator, for v10, with ESRI GRIDs. Not sure if it's the same for v9.3, or for other formats.
Thanks i am using ver 10 as well, i used this it worked without the " ", i just wrote con(isnull(myraster.tif),0,myraster.tif) and it worked one time and that was it, it stoped again, is there any syntax error in my used format?