At first, the original Win98 was never supported by A6. You need SE at least.

6.50 crashed under Win98 when you set the video resolution to a value not supported by the 3D hardware. This was fixed with 6.60.

Both A6 and A7 run fine under Win98 SE. Nevertheless we've removed Win98 from the list of systems 'officially' supported. Such ancient systems are usually too low in memory and not properly configured to run a DX9 application at all. I suppose that most A6 and A7 projects won't run on 90% of all still existing Win98 systems, for various reasons. That's why we don't officially support it anymore.

In most cases you can see the crash reason in the acklog. Still, I recommend when you publish an A6 or A7 project not to tell your users it's Win98 compatible, even though it is.