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I'm not a SQL Server person but I would expect the registry to have the fold locations where it was installed:<br />
<a href="https://docs.microsoft.com/en-us/sql/sql-server/install/file-locations-for-default-and-named-instances-of-sql-server?view=sql-server-2017" rel="ugc">https://docs.microsoft.com/en-us/sql/sql-server/install/file-locations-for-default-and-named-instances-of-sql-server?view=sql-server-2017</a>
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I'm not a SQL Server person but I would expect the registry to have the fold locations where it was installed:
https://docs.microsoft.com/en-us/sql/sql-server/install/file-locations-for-default-and-named-instances-of-sql-server?view=sql-server-2017 [https://docs.microsoft.com/en-us/sql/sql-server/install/file-locations-for-default-and-named-instances-of-sql-server?view=sql-server-2017]

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No. I changed the path for the engine and databases during installation.
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No. I changed the path for the engine and databases during installation.

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I understand you changed the paths on install. &nbsp;I'm betting the registry has the location of something stored somewhere that will give you the drive letter.
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I understand you changed the paths on install.  I'm betting the registry has the location of something stored somewhere that will give you the drive letter.

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I imagine I need help for that
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Really? &nbsp;You needed help on how to search the registry?<br />
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The link I provided had the PATH to local the SQL Server paths.
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Really?  You needed help on how to search the registry?

The link I provided had the PATH to local the SQL Server paths.

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I unplugged one of my external drives where I have MS SQL Databases installed. When I plugged it back in the drive letter changed and now it can't find the MSSQL server or the databases.<br />
I can open SSMS but it cannot connect to the server. <br />
Is there a way to know which path its looking for ? &nbsp;This way I can rename the drive letter to the original
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I unplugged one of my external drives where I have MS SQL Databases installed. When I plugged it back in the drive letter changed and now it can't find the MSSQL server or the databases.
I can open SSMS but it cannot connect to the server. 
Is there a way to know which path its looking for ?  This way I can rename the drive letter to the original

Find path to the SQLEngine and the databases

Databases are organized collections of data, most commonly accessed through management systems including schemas, tables, queries and processes that allow users to enter and manipulate the information or utilize it in other fashions, such as with web applications or for reporting purposes.

Databases

Microsoft SQL Server is a suite of relational database management system (RDBMS) products providing multi-user database access functionality.SQL Server is available in multiple versions, typically identified by release year, and versions are subdivided into editions to distinguish between product functionality. Component services include integration (SSIS), reporting (SSRS), analysis (SSAS), data quality, master data, T-SQL and performance tuning.

Microsoft SQL Server

This topic area includes legacy versions of Windows prior to Windows 2000: Windows 3/3.1, Windows 95 and Windows 98, plus any other Windows-related versions including Windows Mobile.

Windows OS

SQL (Structured Query Language) is designed to be used in conjunction with relational database products as of a means of working with sets of data. SQL consists of data definition, data manipulation, and procedural elements. Its scope includes data insert, query, update and delete, schema creation and modification, and data access control.