5.0 Hangs at "Installing Windows" - Need to restart install process

Hi

New (fully paid) install of 5.0 on a new IMac.

Hangs at "Installing Windows" with (C:\WINDOWS\setuperr.log) fault. I can't get past this screen as "close" starts up windows and ends up with the same message all over again.

Details of error : Installation Failed: D:\I386\asms. Error Message: Manifest Parse error : Invalid at the top level of the document.

I think the XP Pro installation disk I am using is faulty/scratched. I have a fresh OEM installation disk available that looks perfect. I would like to rollback the XP Pro installation in order to re-install, but can't find help anywhere on how to do this.

Can you advise?

Many thanks

Nigel King