Delete C: partition or just install new OS over it?

I currently have XP MCE and I want to install XP Pro. I am at the partition screen where it wants me to select the partition to install the OS on. Do I first delete the primary partition where the old OS is installed onto, or do I just install over it? I was confused because it says if you delete the partition you... show more I currently have XP MCE and I want to install XP Pro. I am at the partition screen where it wants me to select the partition to install the OS on. Do I first delete the primary partition where the old OS is installed onto, or do I just install over it? I was confused because it says if you delete the partition you may loose any data provided from the manufacturer. Does this mean drivers and such? And if I just install over without deleting it says installing a second OS is not recommended.

Thank you for your help on this.
Update: If I do delete it, will everything work properly when the new OS is installed?

If I don't delete, will installing the OS format that partition anyway?
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