hiberfil.sys: is a file used by Windows when you choose to 'Hibernate' the system. Take a look at this site on how to delete it, if you won't use the Hibernate option. In short, you run
powercfg -h off in a command terminal with administrator privileges. The file should then be automatically deleted, and the Windows hibernation feature disabled.
pagefile.sys: is the file used by Windows to be your Page File, or your virtual memory swap. If you have 1 GB of RAM and want to use 2 GB as your memory, Windows will create a 1 GB virtual memory in your HD and use it as needed. See this site on how to delete it.
Can you delete them? Yes, but not by simply going to the Windows Explorer and removing them. Take a look at the provided links, or do some research about your Windows version, to know how to delete them.
Notice that simply deleting them is not enough: you'll have to disable the hibernate option and the virtual memory use of your Windows.