Pinwydd: I bought and installed both games a few days ago.
Tested if my laptop could handle running them and they worked just fine, even on the highest settings.

Then I went on and played Uru for 16 hours over several days and it ran smoothly all the time. Finished the base game and stopped there.
A few hours later I booted the game up again to continue with the expansions but the graphic settings seemed to have reset and the game lagged so bad it has become unplayable.

I tried lowering the graphic settings and restarting the game several times but it made no difference. Launching it in Compatibility mode didn't help either and I even reset Windows just to be safe. The drivers are up to date as well.

Myst V has now the same problem too as the lag makes it unplayable. Granted, I tested it only for few minutes when I installed it, but Uru I played for several days without a problem so I'm not sure why it suddenly stopped working.

Any suggestions on how this could be fixed or at least what the problem might be?

Edit: I re-installed Myst IV since that one worked fine too a few days ago, but now I receive an error message that my laptop doesn't have the minimum requirements and won't even launch anymore.
Tried also Kynseed and it still works but only in window mode with a notification that the graphics card doesn't support it.