Just in case you have the same problem.The latest Avast anti virus program update is causing a lot of Blue Screen of Death problems for many users on Win XP.
The main error is with fssfltr_tdi.sys
Until Avast bring out an update: - start in safe mode - F8 when booting , then navigate to C:\Windows\System32\fssltr_tdi.sys and delete the file, then reboot normally.
Avast will then finish it's program update which may take a while.
fssfltr_tdi.sys is part of Windows parental control and can be safely removed and can be added again when Avast sorts this problem .