Time to check this cool little MS-DOS computer from 1983. It may run MS-DOS, but it's not IBM PC compatible. This machine has some faults which I have to find and repair. Let's get right to it!
Extra info from HP.com:
The HP-150 was introduced with twin 3-1/2 inch HP 9121 disc drives—the first commercially available 3-1/2 inch floppy-disk drives in the United States. These drives were less expensive, more reliable and held the same amount of information as the 5-1/4 inch IBM-compatible drives.