We can't help without more information. What make and model of computer? What do you want to do with said partition? Do you need to reset your machine to the factory default state, wiping out all your programs and data? That's what a reset partition is for.
Normally at boot time, before windows loads, you will see something like "F12-recovery" or something of the sort. Press the designated key and it will boot into the hidden (recovery) partition.