Unless your system shipped with a recovery partition built in that will allow you to
restore the system back to factory settings then you will need the recovery cd.
During the startup normally at the manufacturer splash screen it will advised you to
press a key combination to perform recovery on the system.
What is the make/model of the system?
If no recovery media is present then you can possibly order replacement recovery
media for the system.
What make you think it is about to crash?