It's been years since I touched 98 but here goes...
I have a working WIN98 system that is running a critical app that I cannot reinstall to a new system. I fdisked and formated a new hard drive, mounted it as drive D:, sys C: D:, and used xcopy32 in a DOS window to move everything from C: to D: . Exit out of Windows to DOS prompt and executed xcopy again.
Installed the new drive in a computer and tried to boot. Get "Invalid System Disk" message. From a boot floppy ran fdisk /MBR. Still no joy.
What have I forgotten?