SQL server 2008 express edition upgrade to Standard or enterprise for sharepoint 2010

Hi,

I have a standalone Test sharepoint 2010 environment for sometime, with       Microsoft SQL Server 2008 (SP1) - 10.0.2531.0 (X64).

Now due to the limitations of the express edition, I want to upgrade the express edition to Standard or enterprise version of sql server in the safest way.

I have read the related articles, but I could'nt find a definate answer, can you please help.

Thanks