I'm gonna take a moment from going old skool and go real old skool with questions about a true vintage beast. I could also have called this "Calling all PC 6300" owners, but I'm not sure just how many here or out there in general have one of these PC Compatibles.

Basically, I have an AT&T PC 6300 machine that was given to me over 10 years ago by the original owners, who were friends of the family and both were university professors.

The Specs are:
8MHz Intel 8086 Processor (w-i8087 FPU)
1x360k Floppy and 10MB Seagate ST-225 MFM HDD
Complete set with proprietary monitor (I think CGA but a bigger plug), keyboard and Microsoft Bus Mouse

Now, before it was put in storage, I remember powering it up and it working fine, but I haven't used the machine in over 8 years. I brought it out from my parents place a couple weeks ago, I recently plugged it in and turned it on, the BIOS appears to be OK but cannot boot to the Hard Drive, saying only "Error loading Operating system".

Now, I would imagine that there must be something wrong with the Hard Drive. The drive sounds fine, so it may just be the condition of the data on the drive, needs a format, etc (hopefully), but in order to do so I need to boot to a floppy and find out.

Unfortunately, I tried a DOS 5 boot disk, which didn't appear to boot the machine. So here's my question:

Does anyone else out there own one of these and had any luck with it, and had any luck running newer versions of DOS(Like 4, 5, 6.22, etc), or are you stuck with the last proprietary DOS that AT&T made available for the system (which I think was AT&T DOS 3.3, a rebranded MS-DOS).

This is a weird system, and from my understanding not a perfect IBM PC clone with a reverse engineered BIOS, but rather a PC Compatible. I'm just curious if anyone knows if any newer versions of DOS run on these or the AT&T disk images are a must.