Data Selection Slow From VB 6.0

Hi
I am using Postgres version
*PostgreSQL 7.4.5 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 3.2.2 20030222 (Red Hat Linux 3.2.2-5).*
for an multy user desktop application using VB 6.0 as a front end toll.

To connect To the PostgreSQL I am using *PostgreSQL Win32 ODBC and OLEDB client drivers 1.0.0.2*

The files included are
Version 1.0 of the PGW32CLI Installer will install the following file versions. Files are installed in a separate PGW32CLI directory so should not conflict with existing applications.
libpq.dll 8.0.2.5098 (PostgreSQL library)
libintl-2.dll 0.11.5.1189 (GNU Text Utils)
libiconv-2.dll 1.8.1134.7927 (GNU Text Utils)
psqlodbc.dll 8.0.0.4 (PG ODBC)
pgoledb.dll 1.0.0.19 (PgOleDB)
libeay32.dll 0.9.7.f (OpenSSL)
ssleay32.dll 0.9.7.f (OpenSSL)

I have server configuration as
P4 3 GHz HT Tech
2 GB DDR RAM,
Intel Original 875 Chipset Motherboard,
73 GB 10 K RPM SCSI HDD x 2 Nos.
Adp SCSI Controller, (You can do software RAID on it)
Server Class Cabinet

Since in the database I have one Major table that Debtor table which is master table and having around 55 lac records. I have set debtorId as a primary key having index on it.I am developing a search screen to search a specific debtor info using this table.

When I fire a query to search a debtor id, it took around 5 seconds to return an answer for a query whether entered debtor id is present in the database or not using ODBC. Where as when Explian the query on the database
Index Scan using tbmstban_debtorid on tbmstbandetails (cost=0.00..6.01 rows=2 width=143)
Index Cond: ((debtorid)::text = '234'::text)

Query for the search criteria is
select * from tbmstdebtordetails where debtorid ='234'

Where as when I am using a like query to search a record starting with debtor id having a characters then it took around 10-15 sec to return a record set having records.
query is
select * from tbmstdebtordetails where debtorid like '234%'

Explain output on the database
Index Scan using tbmstban_debtorid on tbmstbandetails (cost=0.00..6.01 rows=2 width=143)
Index Cond: ((debtorid)::text = '234%'::text)
Thanks & regards,
Mahesh Shinde
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