Thanks for the reply. I registered on the other forum but am still awaiting approval. Meanwhile, I've figured out it's a general problem with Server 2003 and not with the "child window". HFSLIP would use cWnd.exe in four occasions: 1) HFSLIP.CMD, which is called from SVCPACK.INF 2) HFSLPGUI.CMD, which is called from a registry key 3) the registry key that calls HFSLPGUI.CMD (it also contains a reference to cWnd.exe) 4) SETUP.CMD inside IE7_INST.EXE (the updated IE7 installer) All four work if the source OS is Windows XP. With Windows 2000, the first three work (the fourth is irrelevant). With Windows Server 2003, all four fail. Edit: Forgot to mention... The first version of cWnd.exe that I tested was 0.4. The problem outlined above exists in version 0.5 as well.