Have you tried using the download mentioned above for the TRS2004 version?
If you have, the fix is potentially risky - it involves replacing a system file.
If you are sure you want to go ahead, instructions are at
http://windowsxp.mvps.org/comdlg32.htm.
Before you do though, if the file is present, try running the following command in the run box:
regsvr32 c:/windows/system32/comdlg32.ocx
or
regsvr32 C:/windows/syswow64/comdlg32.ocx
You should get a confirmation message when it has registered the file.
Shane
EDIT: As you are running Windows 7, you need to do things slightly differently with the command(s) above:
1.Type 'command prompt' into the Start menu
2.When it appears, right-click it and click Run as administrator.