Not problem, just a solution that I wanted to share.
Dialogs have rounded edges in Windows 7 and I have several screenshots in my gallery. Filling these corners simply with white didn't look nice IMHO, so I made them transparent (with a png). But the rounded corners still looked strange because they received the "drop-shadow" effect is if they were not round. This can be solved by modifying drop-shadow.png a bit (here's my version).
If you didn't understand a word of what I'm saying, just visit my screenshot gallery and look closely at the corners of the screenshots.
