Hai ,
I have install the oracle 10g express edition and oracle Jdeveloper edition in window xp (Oracle express in directory D and JDeveloper i directory C)
when i connect the JDeveloper with Oracle 10g database , the error have occur:

Listener refused the connection with the following error:
ORA-12505, TNS:listener does not currently know of SID given in connect descriptor
The Connection descriptor used by the client was:
localhost:1521:ORCL
So , i think when we install oracle , there have some thing must
be concerned so that this error will not happen !
Any one have idea about it ?

Make sure the oracle DB listener is running and input correct SID in connection description.

I never used JDeveloper. However: is there a TNSNAMES.ORA file somewhere in JDeveloper's directory (or one if its subdirectories)? If yes, I suppose that it doesn't contain entry for your XE database. Try to copy contents of XE's TNSNAMES.ORA into JDeveloper's TNSNAMES.ORA - then run JDeveloper again and connect it to XE. What happens?