Once every year or so.
I just keep a ghost image with my core programs + updates installed so once that's been put on, I just need to install any new updates and any games I'm playing and away I go. Completely finished in less time than it would take just to format and install XP.
I'm a bit confused about this. Though my list of apps isn't as huge as Snowdog's its pretty huge and I'd hate to spend so much time getting things just as I want again...
So just sticking the image back on seems ideal... But doesn't that defeat the object? Isn't the point of a re-install that you start with a new slate?
Quite sure I'm missing something here.