Jerome Fine replies: First, you have not mentioned which operating system you wish to run. There are easy locations to find for some of the operating systems and others are more difficult. Second, if this is for hobby use, you should really be running any PDP-11 operating systems under SIMH - unless you have a legal license to run the operating system that you are looking for. Be that as it may be, there are a number of .DSK files (most of them are compressed via WinZip or at least WinZip will UnZip them) available for download. But the only ones I know about are for RT-11 and they are only to be legally run with SIMH. One thing I don't understand is why there is a preference to use a .TAP file when an emulator is being used. I would think that an image of a hard disk distribution which has random access to all of the files would be easier to use. In RT-11, that image file may be set READ ONLY or WRITE PROTECT so that no changes can be made. For an operating system which requires WRITE access, first make a copy. If you have more information, it will be possible to answer specific questions. Sincerely yours, Jerome Fine -- If you attempted to send a reply and the original e-mail address has been discontinued due a high volume of junk e-mail, then the semi-permanent e-mail address can be obtained by replacing the four characters preceding the 'at' with the four digits of the current year.