In all due respect, my friend, you've caught yourself in a time warp and now it's starting to catch up to you.
You've moved on to a compiler/etc setup that postdates your Operating System by more than a decade. The Winodws Libraries and Headers appear to correspond most closely with Vista... and this means there are bucketloads of stuff in them that will compile/link quite happily and then crash like crazy on your operating system, because the underlying DLL code simply isn't there.
You will also begin to find tools, like POLIB, that won't even run on your old OSs... 64 bit Windows won't even run 16 bit code anymore and version lockouts are becomming more and more common. None of my software (even the free stuff) will run on any OS before XP-SP1 since most of it us using API calls that simply didn't exist before then, so I block them to prevent crashes.
It would seem that your problem with my AddIn was merely the first sign of things to come and it's bound to get continually worse for you as time goes on. In fact, it's even starting to happen with XP users... as quite a number of Vista/7 only apps are now out there... Windows 8 will make it a lot worse since the UI has been substantially
trashed reworked.
The thing is that when you are working with antique systems you really should be working with headers and libraries that closely match that version of the OS and in this case that means you probably should be working with Pelles C 3 or 4, certainly not 7. (You can get older versions...
HERE )
In nothing more than a sincere desire to help you, I do have to wonder why on earth you are so horridly opposed to updating your systems.
I understand from our past conversations that you have a long series of softwares installed that you don't want to have to reinstall... and I'm guessing it's because you don't have the distributions of the software. Thing is with a new OS you would likely discover newer versions of the same software or other packages that do the same things for you. Except this time... you need to archive the distributions away on an external hard drive or DVDs so you have them in case you need to reinstall.
XP is very flexible. It was meant to heal the wound ME caused and it will run on almost any 32 bit PC. It is also the most compatible with Linux Wine. There are tons of drivers out there and most hardware manufacturers are still updating for XP. Most freeware and shareware still runs fine on XP (I've only run into one problem, with a Codec, and it took me about 6 seconds to find an XP compatible version). Literally anything that works on 95, 98, ME, 2000 is going to work on XP... it can also use win2000 drivers.
All this began with your objection to my use of "Visual Styles"... I'm sorry to be blunt, but that's a terrible reason to not update your systems. They can be turned off with nothing more than unchecking a box in the System -> Performance -> Advanced dialog. From there, XP looks just like Win2000... except it doesn't crash when it encounters controls that use VS.
Your problem is only going to get worse with time and I'm thinking all your excuses not to update your systems have pretty much evaporated.