Ganusha
By default when you install the Personnel Oracle, it will start running as a service in your Win2k or WinNT. Check up the service name it will be either ORCL (it is also the SID for your (ONLY ONE) oracle database).
Or you may give try with LOCAL as the host string.
Please let me know if it works, so that I can also confirm this in future.
Thanks
Ganesh