Why add extra variables?
Code:
Private Sub GetWinVerInfo(ByRef plngMajor As Long, ByRef plngMinor As Long, ByRef plngBuild As Long)
    CopyMemory plngMajor, ByVal &H7FFE026C, 4
    CopyMemory plngMinor, ByVal &H7FFE0270, 4
    CopyMemory plngBuild, ByVal &H7FFE0260, 4
End Sub
Unless you're exporting to non-VB callers where you might get a null pointer; but then

If VarPtr(plngMajor) Then CopyMemory plngMajor, ByVal &H7FFE026C, 4
etc