The drives are still functional and pass all tests. MiniTool Partition wizard shows them and the partions but the label is "*:" for both HDs.
Now neither Ubuntu nor Windows detect either hard drive. I have tested both for errors with several programs and both test out OK on all tests. Both show about the correct number of GBs.
I cannot "unhide" either using MiniTool Partition Wizard - although they show up as drives (labeled " *: ") the hide/unhide menu is grayed and cannot be selected. Same thing for attempts to split the partitions: split is grayed and cannot be selected.
The file system is "unallocated" and I can't find any way to change it to NTFS, FAT32 or anything else.
The HD's appear to be perfectly good but I cannot find any way to use them, neither for Ubuntu nor for Windows.
Something that happened during the installation or uninstall of Ubuntu rendered both HDs unrecognizable to both Ubuntu and Windows (which don't even detect them at all).
How can I correct whatever Ubuntu changed to make them recognizable to OS's again?
PS IMHO this clearly IS an Ubuntu issue: every reputable program I've ever seen has an uninstall feature. Ubuntu owes it to those who try it to make it possible for them to uninstall it if they decide to not use it.