China DOS Union

I haven't run into the OP's situation before, so I can't provide a directly effective method, but after summing up the methods from the brothers above, here are a few solution ideas for your reference:
1. Since CMOS can detect the hard disk, and when connected to another machine it can be recognized and used, it can be confirmed that your boss's hard disk itself does not have a hardware fault. If you suspect a CMOS setting problem, you can restore the factory CMOS settings, then try automatically (Auto) detecting the hard disk (this will automatically set the hard disk parameters);
2. Drive C may not be the active partition, so the boot loader cannot find the active partition and thus cannot load Windows. The solution is to boot the system with a Windows 98 boot disk, then load FDISK. After entering the options menu, choose the second item to set drive C as Active.
3. If you suspect the master boot record is damaged (usually the ending signature 55AA is missing), you can use FDISK /MBR for a simple recovery.
4. Personally I think the possibility of partition table damage is not high, because since it can be used on another machine, the partition table is most likely normal. If you really suspect it, you can use DiskMan or the DOS version of KV3000 to recover it.

Thanks, everyone. My problem has already been solved. The method I used was to first repartition with FDISK, and then reinstall the system. Hehe, it took quite a bit of effort!