Every so often we come across a client who wishes to upgrade from a SalesLogix instance setup on SQL 2000. This discussion usually comes up when we start the process of analyzing hardware requirements for the upgrade. Here are a few key points that come up in order to help with understanding the issues you could potentially run into.

Server considerations:

SalesLogix 7.5.3 supports SQL 2005 & SQL 2008. Refer to the SalesLogix compatibility checklist for more details. Most of our clients are on SQL2005, which makes it easy to detach such a database and attach it to a SQL 2008 environment.  
If you are on an older version like SQL 2000, then you will have to attach it to a sql2005 instance which should upgrade it to SQL2005 format. Then repeat the same process to attach the database to SQL 2008.
 
If you don’t have a SQL 2005 environment, it is always possible to setup the free SQL2005 express edition and use that for the intermediate step. Keep in mind though that there is a 4GB database limit on the express edition. For larger databases, you will need a standard 2005 SQL Server edition.  
You could also use the SQL2008 migration tools for this, but you will need the SQL2000 environment running in parallel with the SQL 2008 environment so that the migration tools can properly analyze and migrate data to SQL2008.

Considerations for client computers:

If the implementation involves a sync server and remote users, then you will need to consider the SQL edition that will be installed on their computers:
 
The standard install files provided by SalesLogix  provide you with a SQL 2005 express edition installation which is convenient if the SQL server on the host is also on SQL 2005.  
If you plan to install SQL2008, then you will need to make sure you have a process to download and roll out SQL2008 express editions to users. The standard remote install looks for a SQL express instance called "SALESLOGIX". So to keep things consistent, it would be best to have the SQL2008 instance be setup with the same instance name.
 
On the client machines that run the windows/LAN client or remote clients, you will also need to get the appropriate SQLNative client drivers installed to match the SQL server that has been chosen.