how can associated sa with a trusted SQL Server connection in sql server 2005?

I want to use sa user login sql server 2005 to visit my database "dotnet20" but when I set the user property in User Mapping, It Report
when I set it, An Error Occur like follow
Cannot use the special principal 'sa'. (Microsoft SQL Server, Error: 15405)
and also when I want to Login sql server use 'sa' user, It Report
Login failed for user 'sa'. The user is not associated with a trusted SQL Server connection. (Microsoft SQL Server, Error: 18452)
how can associated 'sa' with a trusted SQL Server connection?

I'm having this exact same problem.

When I login using Windows authent. I can connect to the DB but cannot ad users or grant permissions.

I can create tables fine, but other than that not much? Any idea.

I basically wanted to enable SQL Authent. as well as windows in the security Tab after right-clicking on my Database, but the Windows login lacks the rights although it was used to create the DB and all.

Help !

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Basically, how can I add my Windows user account to the sysadmin role.

I couldve used the default sa account but whenever I login in SQL Serv authent. mode using 'sa' and blank Pwd on the SQL Serv Mngmt Studio Express CTP, on the 1st attempt, it says smthg. like

Cannot connect to INSPI6K\SQLEXPRESS.

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ADDITIONAL INFORMATION:

A connection was successfully established with the server, but then an error occurred during the login process. (provider: Shared Memory Provider, error: 0 - No process is on the other end of the pipe.) (Microsoft SQL Server, Error: 233)

For help, click:http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&EvtSrc=MSSQLServer&EvtID=233&LinkId=20476

Upon trying again just says

Cannot connect to INSPI6K\SQLEXPRESS.

----------
ADDITIONAL INFORMATION:

Login failed for user 'sa'. The user is not associated with a trusted SQL Server connection. (Microsoft SQL Server, Error: 18452)

For help, click:http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&EvtSrc=MSSQLServer&EvtID=18452&LinkId=20476

when I changed the Network protocol to Named Pipes or TCP/IP I got

Cannot connect to INSPI6K\SQLEXPRESS.

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ADDITIONAL INFORMATION:

An error has occurred while establishing a connection to the server. When connecting to SQL Server 2005, this failure may be caused by the fact that under the default settings SQL Server does not allow remote connections. (provider: SQL Network Interfaces, error: 28 - Server doesn't support requested protocol) (Microsoft SQL Server, Error: -1)

What's happening? Why can't I login as 'sa' ?

Please tell me all U DBA-gods out there...

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One f the suggestions I recvd. was to hack the registry, and change theLoginMode of the SQL Server 2005 Express.

Any idea how to go about it, and which Reg. key to change for enabling mixed authentications(SQL & Windows), instead of just Windows auth.?

I saw this article but couldn't find that key

http://support.microsoft.com/default.aspx?scid=kb;en-us;285097

Thanks

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OK I finally found theLoginMode key by searching the Registry and changed it to 2 (original value was 1)

Required a Restart, for it to take effect.

Thankfully not getting thetrusted connection error anymore.

But now it's whining about the password.

AFAIK I never set any Pwd for 'sa' account, yet executing sqlcmd on command prompt throws error

Password Msg:18456

Is there any way to reset the sa PWD? What's the way out?

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Phew! The problem has finally been resolved.

What a nightmare... all due to installing SQL Server 2005 Express on top of existing MSDE (from VS 7.0)

Seehttp://forums.asp.net/1222469/ShowPost.aspx for further details.

and with some help from this articlehttp://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=124596&SiteID=1

Thanks.

Moral of the story: Always unninstall previous versions. Better safe than very sorry !