To my knowledge there is no easy way to create a single centralized alias for a SQL server instance.
You can create aliases in the SQL client, but these have to be created on every client machine, so that's not much help.
I'm also not sure if your alias can even be formatted as a named instance in that scenario. Actually, you can make an alias appear as a named instance.
In any case you're much better off updating the configs.
Based on your comment, yes I misunderstood.
In that case a SQL alias is the way to go. You can use SQL Server Configuration Manager if it's installed, but if not you can use the SQL Server Client Network Utility (cliconfig.exe).
If it's not working, one thing to check is the platform. There's a separate version for 32 bit and 64 bit if you're on a 64 bit system: