no you do not have to be an admin to install windows if you get youir own disc.
if you by XP full you can just boot up with the disc in the drive from there follow the prompts and you can reformat your drive and do a nice clean install.
are you going to get XP or are you going to get 98se or something else, if you get 98/se you will have to make a boot disc to format your drive first then you can install 98/se.
if you can try and get yourself XP although it is expensive sadly
