Windows – oracle XE on windows XP stopped working

I know this will be greeted with derision, but yes I'm running Oracle XE on Windows XP. Long story involving office policies and VMs.

Actually it's been working fine for a couple of years, but today I noticed I couldn't connect – I was getting ORA-12505, ORA-12541 and ORA-12560.

It soon transpired that the DB itself, not the listener, had stopped. Looking in services.msc, 'OracleServiceDB' is listed as not running (even though it's set to start automatically). Restarting it gives me a windows error: 'Error 1067 – the process terminated unexpectedly'. The event viewer shows several instances of the DB stopping by itself.

The only change I can think of which might have caused it to break was the installation of windows XP service pack 3 a couple of days ago.

I'm running windows inside a VirtualBox VM. There is plenty of disk space.

Any thoughts?

I looked in the log and found this:

Fatal NI connect error 12638, connecting to:
 (DESCRIPTION=(LOCAL=YES)(ADDRESS=(PROTOCOL=beq)))

 VERSION INFORMATION:
TNS for 32-bit Windows: Version 11.2.0.2.0 - Production
Oracle Bequeath NT Protocol Adapter for 32-bit Windows: Version 11.2.0.2.0 - Production
Time: 04-NOV-2013 17:48:03
Tracing not turned on.
Tns error struct:
  ns main err code: 12638

TNS-12638: Credential retrieval failed
ns secondary err code: 0
nt main err code: 0
nt secondary err code: 0
nt OS err code: 0