how can i change my os from vista to xp?

[roi]

My friend got a new computer, preinstalled with vista, and now she have to change it to xp and needs my help. I've never done this before until now. I burned the image, booted the cd and now have to partition my drives. I assume this is like some kind of formatting. My question is am i just supposed to partition/format my main drive C or am i supposed to partition/format both my main drive and the recovery drive D. Will partitioning/formatting the recovery drive get rid of critical system processes? What am i supposed to do? Partition/format drive D or not?

Thank you for the help

[KristoferB]

if you're just replacing Vista then why do you need to partition anything? I don't understand that..

does she want to get rid of vista altogether? If so then just format the hard drive, when you put in the Windows XP installation disc it will give you an option to format the disc, just let it.. and obviously formatting the disc will delete everything that's on it so if there's anything she wants to keep transfer it to another computer, usb drive etc