Hi,
It seems your connection string must not be correct.
I assume the Vista machine is your local machine and your mojoportal is running on the same machine as SQLExpress so its not a remote connection issue. Your local machine should have the connection string different from the one on webhost for asp, it will have localhost instead of the ip address, I would remove the port from the connection string unless you configured your SQLExpress to run on a custom port its not needed. If your SQLExpress installation is a default instance instead of a named instance then you would remove the \SQLExpress from the connection string and just use localhost ie the server name. If it is installed as a named instance but has a different instance name than "SQLExpress" then you need to replace \SQLExpress with \WhateverYourInstanceNameIs.
I recommend use a sql user not a windows user for your connection string, so you have to make sure SQLExpress is configured for both Sql Authentication and Windows Authentication. Open SQL Server Management Tools and right click the top node and choose Properties, on the Security section you can enable this. Then create a new sql user and put it in the dbo role for the mojoportal db and then specify this user in your connection string. You can also review the Connections section whether to allow remote connections but really if its on the same machine its a local connection.
Since its a local connection I don't think the firewall is at fault but I don't rule it out either.
Hope it helps,
Joe