I just installed SQL 2008 on a machine and when I run my website to add some data via a form, the browser says COMPUTER92/SQLSERVER can not login to database "mdbb" (computer 92 is my computer name) its is a valid Login under the server security -> logins for the server and the login COMPUTER92 says under its properties that its mapped to "mdbb" but under the users for "mdbb" it doesn't show COMPUTER92/SQLSERVER as a user! Any ideas?
It seems a little confusing to have a user with the same name as your database instance unless I am reading your error wrong. Does it have a username in the error message as well?
As you are using a trusted connection I would say that you need to check what user your website is running under. If you are running iis 5.1 (Win XP) then it will probably be ASPNET for iis 6 you can check this in the identity of the application pool I think by default it is Network Service but I am not certain.
I noticed that you're referring to your server and instance using a forward slash - "COMPUTER92/SQLSERVER", but you actually need to use a backslash - "COMPUTER92\SQLSERVER". It's a longshot, but could this be causing the problem. Also, if you have SQL Profiler installed, can you run a trace and see if you see the connection attempt or the user's error message?