> Am I right in assuming that the you-beaut OS/2 you-beaut 
 > protected you-beaut mode etc is meant to actually stop one 
 > application (e.g. WinOS2) from crashing all the other 
 > applications?

No. The "crash-protection" IBM list as a feature refers to the
interaction of multiple 32bit protected mode applications. It works
remarkedly well, with the only problem remaining being OS/2 apps which fail
to respond to system requests - which tends to put a halt to the DeskTop
(the kernal runs along fine and regardless including background tasks).

 > I have attempted to run an application from CDROM under OS/2 
 > 4.0, WinOS2 fullscreen.

When running DOS (16bit realmode) tasks, your must be subject to the
limitations and problems of the particular application code. OS/2 treads a
fine line between allowing/disallowing hardware access and task
interaction, and decreasing levels of DOS compatibility.

The basic rule is; if a DOS or Windows app appears to cause problems on the
system, AXE it and find another. After all there's enough to choose from
:). Heck these days there's plenty of OS/2 apps to choose from, and Windows
apps are best avoided because of 1) this problem potential, and 2) their
much heavier load on the system.

 > P.S. Third time it worked fine, no difference (that I am 
 > aware of) between the 2nd and 3rd runs.  Between the 1st and 
 > 2nd runs one change was that there was no CDROM changes done,
 >  because for the 2nd run I rebooted with the correct CDROM 
 > already in the machine.

There's a long list of little things that Dos/Windows apps can want or
require. e.g. a printer installed into WinOS2, MMediia installed into
WinOS/2, multiple after market video utilities installed into WinOS2,
particular screen resolutions, particular memory settings (EMS, and/or XMS,
and/or DMPI), etc etc etc. Any of these could see your app working as
designed. Given the need these can be explored, but as I say, it's much
easier to simply use an OS/2 application designed for the same job.

Regards.
--- Msgedsq/2 2.2e