Running our Excel97 under WIN8.1 leads reliable after some starts to the
problem that after starting Excel97 even with a new empty sheet the app
hangs up in a way that if a cell is clicked and the focus is set to this
cell there seems to be no release of mouse, and moving the cursor spans up a
selected area as if the mouse was still pressed down, and there is no escape
except killing the task by the task manager (only Strg Alt Del ist a
recognized keystroke).

If after startup and showing the new empty table instead of a cell click one
of the default three sheet tabs is clicked the mose pointer shows an arrow
with an empty rectangle, no action takes place, no menu or keystroke is
executed, and there is also no escape except killing the task by the task
manager.

Wenn Task Manager is called and cursor is no longer assigned to the Excel
Windows all other programs work well without any problems.

Excel97 shows this behaviour with an empty startup sheet as well as after
startups with a given fullfilled data sheet, but when this data sheet is
opened by Open Office, f.e., and restored using .xls format there is a great
chance that Excel97 starts correctly next time, despite of loading an empty
or an existing data sheet.

Best method to get a correctly running Excel97 is to restore a system image
even if there was no Windows update or any installation since last restore.

It doesn't look like a simple compatibility problem: First, after restoring
the system image original EXCEL.EXE has not assigned a compatibility
selection in the file manger's property dialog, so all Excel starts invoke
an unchanged exe, and once the problem occures a compatibility mode change
to Windows XP or any other version doesn't help.

Has anyone an idea what I could try?

Due to internal reasons I must run WIN8.1 and cannot upgrade Windows as well
as Excel (we have newer Excel versions as well as Windows versions, would be
the easy way) but in this special case we have to use WIN8.1/Excel97 only.