As liveware2000 said, to install the comdlg32.ocx file for Windows 7 x64, you can download the file (link is above) and put it in the Windows/SysWOW64 folder. Then, in command prompt or in Start->Run, type
regsvr32 %Systemroot%\SysWOW64\comdlg32.ocx
(and hit Enter, of course)