Universal way to open FDF file once it has been generated?

I currently have a vb form (vs2008) which pulls information from a SQL table. It then generates a FDF output of certain information on the form, and then opens the FDF file which then merges back in with the PDF file. I have this fully working on a Windows XP machine, but I cannot get it to work properly on Windows 8. I have tried defining the path but I'm concerned that different versions of Adobe Reader could lead to problems later when the app is installed.

My code for FDF output:

  Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim FdfAcX As FDFACXLib.FdfApp
    FdfAcX = CreateObject("FdfApp.FdfApp")
    Dim fdf As FDFACXLib.FdfDoc
    fdf = FdfAcX.FDFCreate
    fdf.FDFSetFile(Application.StartupPath & "\Enquiry Form - Company.pdf")
    fdf.FDFSetValue("lnamount", LoanAmount.Text, False)
    fdf.FDFSetValue("estval", EstimatedValueTextBox.Text, False)
    fdf.FDFSetValue("loanpurpose", LoanPurpose.Text, False)
    fdf.FDFSetValue("term", LoanTerm.Text, False)
    fdf.FDFSaveToFile(Application.StartupPath & "\Enquiry Form - Company.fdf")
    Command2_Click()
End Sub

Which links to the code for the FDF open:

Private Sub Command2_Click()
    Dim file As String
    file = Application.StartupPath & "\Enquiry Form - Company.fdf"
    Process.Start(file)
End Sub

which works on Windows XP, but not on Windows 8. Please Help, it's driving me mental.

When I run the app on Windows 8, it runs fine and pulls from SQL correctly, however when I go to click on the button, I get an unhandled exception error.

Happy to post the error if needed.

I have figured out the problem. The issue is that FDFACX.dll will not register as it should in a Windows 8 environment. My solution was to run command prompt with Administrator access and manually register FDFACX.dll. My app now works. I hope this will help someone else with a similar issue.