You will need to Format the C partition then use a Disk/Partitioning program to get rid of the 100MB System Reserve partition and combine it into the C, FIRST, partition on the drive then install XP and all you program.
That is "IF"
you system, all the hardware, has XP drivers
available for it/them. If not then you are kind of stuck with Win 7. But you can make it act and look like XP with Classic Shell.