Hi, Barbara and thanks for your reply.

I include the comctl32.ocx in the directory from which Setup Wizard reads the files and makes the distribution set. And my OCX successfully registers itself during the installation. BUT - on my machine there's COMCAT.DLL version 5.0 and the appropriate OCX, while on the computer, on which the problem occurs, version of COMCAT.DLL is older - 4.71 and my version of OCX. Even if I copy 5.0th version of COMCAT.DLL, it doesn't help and when I try to REGSVR32 C:\WINDOWS\SYSTEM\COMCAT.DLL it says that it was impossible to register it. I may replace the treeview control on my form with the old one, (and i'm pretty sure that it WILL help) but why should I?

Best regards, Uri.