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when i attempt to download ms dos 7.1 and do the restart to install, it prompts me with Invalid system disk.
MS-DOS 7.1 was never released as a standalone product, it was part of Windows. You create (or download a previusly created) bootdisk on such a system.
I am pretty sure, there were no 2 disk "versions".
So when talking about this "release", people really should know, which DOS-disk you are using.
There was no official installer, people have written these themselves.
@sdose i think OP is referring to the China DOS Union distribution of MS-DOS 7.1 available in the Library.
"Invalid system disk" relates to attempting to boot to a non-bootable floppy. Either change your BIOS to boot to the hard drive or eject the drive and restart.
Another reason is that you're probably trying to boot off the second disk. Make sure you're booting off the first one to install DOS.
I've made this mistake many, many times, with a ton of head-scratching (and sometimes swearing) accompanying it. Checking the disk you're booting off of makes a HUGE difference.
The original poster needs to add MUCH MORE information about their problem and configuration. Otherwise we are just blindly guessing.