[The Fifth Horseman]

If you bothered to read the technical notes, you'd know that a) it's a DOS game and b) you're supposed to run this game using DOSBox instead of running it directly in Windows.
Because they're no longer compatible with Windows and running them can result in your system spontaneously freezing or rebooting.

Further, all archives placed on Abandonia are thoroughly checked with antiviral software - thus, I find your allegation unlikely.

The normal "The system has recovered from a serious error" message does not have anything to do with viral infections. It's far more likely to have something to do with you killing the power when the operating system was loading.

If you're getting one that specifically states "this error caused by spyware and viruses on your computer", that message itself is produced by a piece of malware which got into your system.