Could you be a little bit more specific, when you say it doesn't safe mode start, does it just say at the choices window? or does it not fully load, or just it blue screen again.
Also if you could give some kind of Error code associated with the blue screen (ex: Physical Dump of Memory, Missing System Root File). That way its easier to determine what exactly is causing the issue.
i am running xp and it keeps freezing and then the blue screan comes up says to try to start in safe moad so i press f8 brings up safe mode and usual stuff but it wont start in safe mode or last known good config y can anyone help please