what sequence do you follow to install a mobo. The board came with an installation cd do you run this before repairing/ installing the OS or visa versa

Wipe your operating system;
Install the new motherboard;
Install the new operating system;
As soon as you can (i.e. before you start tweaking OS settings, etc), run the installation program off of the CD to install the motherboard drivers;
Install your other drivers, e.g. graphics card, that may rely on your motherboard being correctly configured first.

thanks for rapid response. How do you wipe the currebnt operating system

The process will depend on what operating system you have and whether you have a Recovery CD with the PC and exactly how it works ... or whether you have an appropriate boot disk.

I've written a couple of articles about this in the D-A-L.com Member's PC Help Articles section of the forum: http://www.d-a-l.com/help/article.php?c=12