Sounds like the Windows Validation tool, possibly kicking in because you've changed some hardware, but I didn't think CD / DVD drives mattered.
Anyway, it should try to connect to the Microsoft website, and ask you to download a small program which validates your copy of Windows. Not sure why it's not connecting, but I think you probably need to use Internet Explorer, and allow pop ups, and if asks for ActiveX permission, allow that too. If you're still having difficulties, as Clive said, Sandra will be along later.