Jerome Fine replies: What does "eric_pdp11_rt11.dsk" contain? If it is a zero length file, then the install will probably not work. Also, I presume that you actually typed: "Boot rl0" since that is where the RT-11 distribution is located. Also, although RT-11 uses "dl" as the device name, SIMH uses ""rl" as the device name. That is the reason for the confusion! And if you want to go through the installation, then I suggest you use PUTR to produce an empty "working" dsk (container) file via the command: FORMAT eric_pdp11_rt11.dsk/RL02 before you "Boot rl0" PUTR with the "/RL02" switch automatically produces a container file with the extra blocks required by a PDP-11 for the system area on an RL02 media. BUT, before you boot rl0, you should probably: SET RL0 LOCK Then, the install will abort because rl0 is WRITE PROTECTED. At that point, you can: COPY/DEVICE DL0: DL1: If you want to avoid the install, just: COPY/BOOT DL1:RT11XM.SYS DL1: BOOT DL1: In your situation, the install is NOT needed. However, "rtv53_rl.dsk" does not have the required system area which is required under RT-11 to: INIT DL0: So if that is ever required, you MUST start with PUTR to set up that empty file and then COPY from DL0: to DL1: which can be done after you Boot rl0: (DL0: as far as RT-11 is concerned) even though no system area is present on rl0: After you exit from SIMH, you might want to make a backup copy (under the Windows OS) of rl1: Once that is done, if you have more RT-11 questions, please ask. 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.