>>(1) The short way is to cast the return result to UInteger, and change the return type of GetCrc32() to UInteger
>
>This line cannot be changed to UInteger:
>
>

>        Dim lnCRC32Result As Integer = &HFFFFFFFF
>

>
>It would give an error: "Constant expression not representable in type 'UInteger"

Yes, it seems vb interpretes those as signed

http://msdn.microsoft.com/en-us/library/s9cz43ek.aspx

Append the type to the constant. U and I

    Dim lnCRC32Result As UInteger = &HFFFFFFFFUI