Hi, It is possible that this is due to the presence of NaN values in your images. You can check this, and remove them if necessary, with fslmaths. If this is not the problem then please send us the whole log file so that we can check that there aren't any earlier problems. All the best, Mark On 5 Aug 2014, at 14:29, Mahsa Alizade shalchy <[log in to unmask]<mailto:[log in to unmask]>> wrote: Dear FSL users Hi As I load "nii.gz" or "nii" images to FEAT(doing a 1th level analysis) I have encountered the following errors: prestat /usr/local/fsl/bin/fslmaths prefiltered_func_data_smooth -mul 0.959388000439 prefiltered_func_data_intnorm ** ERROR (nifti_image_read): failed to find header file for 'prefiltered_func_data_smooth' ** ERROR: nifti_image_open(prefiltered_func_data_smooth): bad header info Error: failed to open file prefiltered_func_data_smooth Cannot open volume prefiltered_func_data_smooth for reading! Poststat usr/local/fsl/bin/contrast_mgr -f design.fts stats design.con ** ERROR (nifti_image_read): failed to find header file for 'stats/sigmasquareds' ** ERROR: nifti_image_open(stats/sigmasquareds): bad header info Error: failed to open file stats/sigmasquareds ERROR: Could not open image stats/sigmasquareds Image Exception : #22 :: Failed to read volume stats/sigmasquareds An exception has been thrown Failed to read volume stats/sigmasquaredsTrace: read_volume4DROI; ContrastMgr::Load; ContrastMgr::run. I tried loading hdr/img version of that image which solves the errors above but prevent FSL from running the registeration part! could you please tell me how to overcome the errors? Thanks in advance. Best Regards, Mahsa