oracle 10g release 2 on windows, forget password

I get an old db from someone who left the company. It is Oracle 10g R2 , but i do not have sys or system password, i have administrator privilege to that windows 2003 server where oracle locates.

I can not do like Solaris
export ORACLE_SID=XXX
sqlplus / as sysdba to change sys or system password

What can I do on a Windows platform?
I tried
ORAPWD file=XXX.dat password=manage

but seems can not work
Any one can help me ??

Thanks a lot.

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