Are you talking about Esri GRID format? If so, what version of ENVI do you run? Do you have ArcGIS installed on the same system? If you are using ENVI Classic or prior to ENVI 5, it requires that a licensed version of ArcGIS is available and then you can open it as a GRID File using File ->Open External File->IP Software->ESRI GRID. Alternately, you can use ENVI Zoom to read in a GRID file and then save it out as ENVI format. Opening a GRID in ENVI Zoom does not require an ArcGIS license because it uses a GDAL library instead. Or perhaps you are talking about another format. I do see there are various types of files with a '.grd' extension. I would need to know more about what type of file it is.

Hi Thank you so much for your guidance. Actually I am using ENVI4.8 and ArcGIS10. I did same way that yo explained, but for me it doesn't work. The message says that need the license. what I must do? Thank you Best, Hadi

Well, yes, you do need a license to run the software. Both ENVI and ArcGIS will need to be licensed. It sounds like there must be a problem with one of those licenses. It's hard to tell which one without more information. To troubleshoot licensing issues, you will want to contact your local ENVI distributor or Exelis VIS Tech Support (303) 413-3920 or support@exelisvis.com, and provide the exact text of the licensing error you are getting. - Peg Exelis VIS