On some occasions, you might find yourself having to carry out a repair of Windows XP.
The process is as follows:

Insert Windows XP CD.
When prompted with the Welcome to Setup screen, press ENTER.
Press F8 to accept the EULA
Select the partition you wish to repair and then press R.

But what if the R=Repair option is not at [...]

I recently received my Windows Vista Business Upgrade through the post.
Microsoft seem to have really wanted to restrict the use of clean installations. With an upgrade licence, when you try to install Vista by booting from the DVD or CD, it will tell you that Vista cannot be installed.
Unfortunately, if you want a clean installation [...]