Every time that you switch your computer on it 'boots', (A term from the mainframe times from a program called the 'bootstrap loader', now incorrectly used on PCs.)
I suspect that what you want to do is reload the Operating System onto your hard disk for some reason or another.
I am afraid that the answer to that question is: it depends. Some PCs have a 'Recovery Partition' on the hard disk and others need a recovery CD and you don't say what you have.
T, October 2009
