If you use Windows platform and FAT32 file system the file size is limited to 4GB. This can cause the problem. Try to convert your file system to NTFS. Hope this helps ---------- In response to: ------------------- We’ve got a serious technical problem on ENVI. We have LISS and PAN images to be processed. The classification is successfully completed in LISS image. But while classifying the fused image the following error comes. "Error: “Error encountered writing to file, Unit:101,File:C:\trial” the result may be invalid”" The size of the fused image is 4 GB, and we have 20 GB of free space in our system with 1GB RAM. What might be the cause of this error? Any help regarding this will be highly appreciated.