I was going through the SQL Server Security Catalog view and stumbled upon the sys.server_principals view. This view contains a row for every server-level principal. When you install SQL Server 2005/2008, the NT AUTHORITY\SYSTEM login gets created. Querying this view, we can easily retrieve the creation date. Here’s how:
SQL Server 2005/2008
WHERE name='NT AUTHORITY\SYSTEM'
SQL Server 2000
where name='NT AUTHORITY\SYSTEM'
If you know of a simpler way to retrieve the SQL Server installation date, make sure to drop a comment.
Note: This query will not give correct results, if in between your master database became corrupt and you had to rebuild it. I will update this post with other such exceptions(as and when I learn about them) when this query may not return expected results.