Outlook Custom Form

We have a custom form that is working on XP but not in vista. The modeless.dialog com object is not found.

Where can I find that com object so I can put it on my machine

Here's the code

' --- the following code had been automatically added to ensure all required COM objects are installed.
function COMExists(name)
' checks whether a specific COM object is installed on
' your local machine
set cwsh = CreateObject("WScript.Shell")
on error resume next
dummy = cwsh.RegRead("HKCR\" & name & "\")
if err.number<>0 then
COMExists = false
else
COMExists = true
end if
end function

if not COMExists("modeless.dialog") then
msg="COM-Object ""modeless.dialog"" is required. This object is currently not installed on your system." & vbCr
msg = msg & "Install the MODELESS component from CD" & vbCr
MsgBox msg, vbExclamation