pagefile.sys is a part of your hard drive used as virtual memory when you run out of physical memory.
hiberfil.sys i think is the settings that are stored when you use hibernation.
i would not delete any of these.
set you swap file to windows managed size in control panel/system/advanced/performance/settings/advanced if you use xp and then set your windows system files to hidden that way you wont delete any by mistake.
use cleanup to safely delete any temp files etc you wish to get rid of click here