Registry file failure

Can anybody help me ? When I switched on my laptop today a blue screen appeared with the message....... 0F00: 136C C 0000218 registry file failure The registry cant load the hive ( file ) system root/ system 32 / configuration / security It is corrupt, absent or not writable Beginning dump of physical memory. I have run every diagnostic possible all day today and every test comes up as Pass with a tick. I am using an Inspiron 6000 with Windows XP Home Thank you.