I don't have a lot of experience with this, but sine no one else has responded I will say that the difference between a regular NOL and an AMT NOL is any adjusments that have to be made for AMT purposes. For example, if the NOL includes depreciation at a faster rate than allowed for AMT purposes, you would have to add back the difference in depreciation in determining the AMT NOL. There are other adjustments possible, but that is probably the most common.