upgrading bootcamp xp to windows 7

I have win xp pro x86 installed on bootcamp and i wish to replace it with windows 7 x64 but i am unsure off a few things.
1. Can i upgrade xp x86 to 7 x64 without loosing all my xp program files etc or do i need to formate the bootcamp partition?
2. When i reformate the bootcamp, will it reformate the mac os?? and how do i do the reformate and installation, do i do it all through mac os bootcamp again or the bois when windows partition starts up???
thanks

You can not update a 32 bit operating system to the 64 bit version. The 64 bit version must be installed clean. So the answer is no. And yes, you will have to reinstall all your programs.

thanks for the info =] so i will have to reformate my bootcamp partition, do i do that by using the mac osx bootcamp installer or can i just boot my windows natively and enter bios selecting load cdrom etc??? or would that wipe my mac partition too?
thanks again for the help

You should be able to do it by first booting into Windows XP. Once in Windows XP, insert the Windows 7 DVD. It should automatically execute and bring up the Windows 7 installer.

Here is where you need to be especially careful! The Windows 7 DVD has both the 32 bit and 64 bit versions to choose from. When you choose the 64 bit version it should give you a warning that it will remove XP before installing.

You need to watch the installation prompts carefully. Make sure you install Windows 7 on the boot camp partition not your OS X partition!

If your Boot Camp partition was previously formatted to FAT-32, the installer will format it to NTFS as Windows 7 can not be installed on FAT-32.

Before starting... make backups. Use Time Machine and additionally use a clone backup to an external drive. SuperDuper or Carbon Copy Cloner are ideally suited. And again, be careful you don't overwrite your OS X installation.