If you're referring to a Recovery Partition which resides on many of the brand-name computers, you can easily research the steps by visiting the computer manufacturer's website.. As long as the hidden recovery partition is not corrupted, as might happen if the hard drive failed, then pressing the appropriate F-key at startup(such as F10 or F11 on HP computers), should immediately take you to the recovery menu on the recovery partition.. It's a fairly straight forward procedure with prompts along the way.
Hope this helps.
How can I reinstall XP on my DELL desktop using the copy of windows that is on the hard drive (hidden parrtition). I do not have XP disk and need to format then reinstall XP.