Adding section to windows programs

[Hero]

Hi all
I write an small program that adds a section to a exe file.But when I tested
on notepad.exe or mspaint.exe,new program crashes.
I first think that my program is buggy,But when I see that the Yoda yC that
protects every normal program correctly(it adds section too) is crashing too,
I think perhaps there is a modification detection on windows programs.
Is my idea is correct?Is there any change detection in this windows programs?

sincerely yours