Windows 2003: auto time sync when CMOS battery is dead

modify registry to anticipate large time difference :
How to configure the Windows Time service against a large time offset
change MaxPosPhaseCorrection and MaxNegPhaseCorrection to 0xFFFFFFF

create schedule to run AT STARTUP that will launch batch file containing these commands :

w32tm /config /manualpeerlist:id.pool.ntp.org,0x8 /syncfromflags:MANUAL /reliable:yes
w32tm /config /update
net stop w32time
net start w32time

set retryCount=0

:SyncStart

if %retryCount == 90 goto SyncEnd

set /A retryCount=retryCount + 1

REM *** Resync the system clock

w32tm /resync

if errorlevel 1 goto SyncDelay

if errorlevel 0 goto SyncEnd

:SyncDelay

REM *** If unsuccessful, delay 10 seconds, then retry

choice /n /t:y,10>nul

goto SyncStart

:SyncEnd

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summarized from :

How can I sync the computer's clock upon startup?

Synchronize Time in a workgroup environment or with a non-Windows time server

alternative tools not tried :
Automatically sync Windows time more often than default