Application stability

I wrote a VB6 application about 10 years ago, which has been kept going on a life support machine since clients upgraded to Windows 7.

The app uses various third part components. If I do not run the app with XP SP3 Compatibility mode turned on, it is unstable and clients receive frequent random APPCRASHes. I am happy to leave the compatibility turned on except for the fact that it seems to break code that uses the ShellExecute API to open files on network shares.

This only happens when the Windows UAC settings are switched on.

When the app is not run in compatibiluty mode, the ShellExecute code runs fine. I have tried writing a VB.net workaround which Starts a process based on the parametres passed to it, but this didn't work as it inherits it's permissions from the calling app.

It seems I am caught between a rock and a hard place with this one.

I either need to find another way of opening files on a network share, OR somehow make the app run smoothly without forcing the compatibility option. Just to find out what is making it crash would be a start. It could be any one of the third-part controls, or even that VB6 is just not that stable in Win7.

I have tried adding a DEP execption on the client's machine, no joy.

I have read many posts (like this one) which recommend the compatibility option as a solution, but I am fast running out of ideas.

Now I see why developers simply say, sorry we no longer support this application, please upgrade!

My ShellExecute Code:

Public Sub ExecuteOpenFile(strFile As String)
10        If Len(strFile) >= 7 Then
20            If UCase(VBA.left$(strFile, 7)) = "HTTP://" Then
30                Call ExecuteLink(strFile)
40                Exit Sub
50            End If
60        End If
70        If Len(strFile) >= 4 Then
80            If UCase(VBA.left$(strFile, 4)) = "WWW." Then
90                Call ExecuteLink(strFile)
100               Exit Sub
110           End If
120       End If
130       If InStr(1, strFile, "@") And InStr(1, strFile, ".") Then
140           Call ExecuteLink("mailto:" & strFile)
150           Exit Sub
160       End If
170       Call ExecuteLink("explorer.exe", Chr(34) & strFile & Chr(34))
End Sub

Private Function ExecuteLink(ByVal FileName As String, Optional CommandLine As String = "") As Long
10    On Error Resume Next

Dim lngResult As Long

          lngResult = ShellExecute(0&, "Open", FileName, CommandLine, vbNullString, 1)
          ExecuteLink = lngResult
          
End Function

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Many thanks in advance for your help.