I am having a similar problem. I loaded Oracle 11g on my Windows Vista PC (Windows Vista Home Premium with Service Pack 1). The install was successful and I can access the database with SQL*Plus and with Enterprise Manager. When I attempt to log in with Pl/SQL Developer I get the following error message:
Initialization error
Could not load "C:\oracle\product\11.1.0\db_1\bin\oci.dll"
OracleHomeKey: SOFTWARE\ORACLE\KEY_OraDb11g_home1
OracleHomeDir: C:\oracle\product\11.1.0\db_1
Found: oci.dll
Using C:\oracle\product\11.1.0\db_1\bin\oci.dll
LoadLibrary (C:\oracle\product\11.1.0\db_1\bin\oci.dll) returned 0
Here is the information from the Support Info window in Pl/Sql Developer:
--- Info ---
PL/SQL Developer
Version 7.1.5.1398
01.48247 - Unlimited user license
Windows Vista (64-bit) 6.0 Build 6001 (Service Pack 1)
Physical memory : 4,194,304 kB (3,118,276 available)
Paging file : 4,194,304 kB (4,194,304 available)
Virtual memory : 2,097,024 kB (1,970,236 available)
Parameters
C:\Program Files (x86)\PLSQL Developer\plsqldev.exe
Preferences
Session mode: Multi
OCI Library: C:\oracle\product\11.1.0\db_1\bin\oci.dll
Use OCI7: False
Preference Files
C:\Program Files (x86)\PLSQL Developer\Preferences\Default\Default.ini
C:\Program Files (x86)\PLSQL Developer\Preferences\Bill\default.ini
Plug-Ins
Aliases
Homes
OraDb11g_home1 (C:\oracle\product\11.1.0\db_1)
DLLs
C:\oracle\product\11.1.0\db_1\bin\oci.dll
TNS File
Using
Home: OraDb11g_home1
DLL: C:\oracle\product\11.1.0\db_1\bin\oci.dll
OCI: not initialized
--- Registry ---
SOFTWARE\ORACLE
SOFTWARE\ORACLE\KEY_OraDb11g_home1
ORACLE_HOME = C:\oracle\product\11.1.0\db_1
ORACLE_HOME_NAME = OraDb11g_home1
ORACLE_GROUP_NAME = Oracle - OraDb11g_home1
NLS_LANG = AMERICAN_AMERICA.WE8MSWIN1252
ORACLE_BUNDLE_NAME = Enterprise
OLEDB = C:\oracle\product\11.1.0\db_1\oledb\mesg
StmtCacheSize = 0
--- Path ---
C:\oracle\product\11.1.0\db_1\bin
C:\Windows\system32
C:\Windows
C:\Windows\System32\Wbem
C:\Program Files (x86)\Common Files\Roxio Shared\9.0\DLLShared\
c:\Program Files (x86)\Microsoft SQL Server\90\Tools\binn\
C:\Program Files (x86)\UltraEdit
--- TNS names ---
The only other thing I noticed is that the bin directory that was created by the Oracle install is in upper case as in:
C:\Oracle\product\11.1.0\db_1\BIN\oci.dll
All of your references seem to be lower case. Hopefully that's not an issue anywhere.
Thanks for taking a look...wjp