window platform problems

help me please.

Currently, my application is complete (bar one or two things) but I'm testing it at the moment for compapiblity with all versions of windows, and I have come across a pretty major problem.

I designed this application (actually two minor applications packaged as one) it was through Windows NT. Used package and install to create a setup program and have tested it on win 95, and also win 98. This is were the problem arises.
Whenever I try to run one of the applications within one of these windows environment's, I get an 'illegal operation' error and shuts down.
Details of the error say;
application caused an invalid page fault in module OLEAUT32.DLL at 015f:7fe83221.
then it starts listing registers.

I have tried changing this DLL but cant through windows-it uses it.

So my question is actually three fold.

First and most important, does anyone have an idea why this happens, is it a problem with my code, i use two extra api's in this application (GetVersionEx, GetWindowsDirectory), could they be the problem.

secondly, does anyone know a good website where i can get info about windows dll's?

Third and finally, to all Win 2000 users out there. Could you tell me where dll's are stored in this os. winnt-system32 folder, win98 & win95 -system folder. An answer to this would be very helpful.

Thank you for even bothering to read this waffle, even more thanks if you can answer any of it.

Cheers big ears!