Joel Spolksy Things You Should Never Do Part 1 http://www.joelonsoftware.com/articles/fog0000000069.html
Darmesh Shah How To Survive a Ground-Up Rewrite Without Losing Your Sanity (a response to essay #1 13 years later) http://onstartups.com/tabid/3339/bid/97052/How-To-Survive-a-...
It's not always cut and dry when you should start over, but if you are make sure you are doing it in a way that starts presenting customer/user value ASAP.