Could not load the DLL xpstar90.dll, or one of the DLLs it references. Reason: 126(The specified module could not be found.)

Hi Team ,
This issue was faced by someone outside IBM but my main intention is to explain the benefit of another nice tool : Dependency Walker (http://www.dependencywalker.com/)

Issue :
SQL Server Agent failed to come up after the service account password was reset at AD level .

Error(s) :
In the event log you will see these errors in sequence :

Description:
Could not load the DLL xpstar90.dll, or one of the DLLs it references. Reason: 126(The specified module could not be found.).

Description:
Failed to retrieve SQLPath for syssubsystems population.

Description:
SQLServerAgent could not be started (reason: Failed to load any subsystems. Check errorlog for details.).

The first error is the main error and rest are the errors following the first error and we need not to think about them .

Troubleshooting and Resolution :
The error clearly says that either there is a problem with xpstar90.dll or the other dlls that this dll references .
This file is located in I first tried to re-register xpstar90.dll by using regsvr32 xrstar90.dll and got this message :

xpstar90.dll was loaded , But the dllRegisterServer entry point was not found.

I have heard that sometimes there is a different way of registering some DLLs , so by this error I did not come to the conclusion that this file is corrupt.
I was also thinking that there might be some other DDL that this DLL refers to , which got corrupted.

I decided to see the tree structure of xpstar90.dll in Dependency Walker . I opened the C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Binn\xpstar90.dll in it and go this output.



So, in this case XPSTAR90.DLL itself was corrupt .I found its version 2005.90.4035.0 and replaced it with another one that I had in another instance .
SQL Agent came online .
In case if it dos not , then we need to uninstall Native client from ADD Remove Programs and reinstall it .

Happy learning
Abhay