I managed to find an old XP SP2 CD and installed it. It took some time but I managed to track down the issue to a critical manifest file parsing issue
in XP SP2. Unfortunately the solutions described in that article do not resolve the issue. As this only happens with an old version of Windows that no one should be using anymore, I am not sure spending any more time on it makes sense.
Then I have interesting news. I applied the WindowsXP-KB921337-x86-ENU.exe hotfix from that article (and nothing else) to my XP SP2 test machine, and the issue was solved. mIRC 7.29 can now be started on it an infinite number of times without problems.
So, I'm curious why your results differed. Did you not apply the KB921337 hotfix, and only re-compile mIRC without the problematic manifest properties described by that article?
Anyway, assuming KB921337 solves the issue for you as well, and assuming that KB921337 is itself distributed by Windows Update to XP SP2 users, this bug report can be discounted (with my apologies for the false alarm).
P.S. I agree with your statement in your first post: I myself would not expect a software author to code work-arounds for issues caused by every level or permutation of incomplete patching across multiple legacy versions of Windows. When I reported this BSOD issue, I simply failed to consider the possibility that the incomplete patching of XP SP2 may have been the cause. Instead, and because it is a common occurrence today, I assumed that you had possibly coded an XP XP3+ dependant function without realizing it. Under that assumption, and since you support Windows 2000 onward, a bug report seemed in order.
P.P.S. On the subject of legacy operating system compatibility in general, count me as someone who appreciates your continuing support of them. I love software with a broad compatibility base. If you intend to continue supporting 2000, you might look into using a VM for hosting a fully-patched-except-for-SP3 installation of WinXP SP2. The reason: there are still more users of XP SP2 than of 2000. Using a VM would also allow you to test mIRC under a fully-patched (SP4+UR1) Windows 2000 when necessary.
P.P.P.S. HorseC, thanks all the same for your interest in helping.