SQL is M/Softs pro database which was probably used at the company that you got the unit from and was part of their network, and that program is used with it. If you are using this for your normal home computer you should delete it to save hardrive space and possibly memory resource. It will be of absolutely no value unless you are prepared to purchase MS SQL and set up a SQL server and network your present computer to it and spend hundreds of hours and thousands of dollars installing and learning SQL Server (I don't think so).

[EDIT]: By the way, I just thought: are you using this computer to work from home, and you connect into your company's network? IF that is the case, do not delete it. You may need it if your company is using SQL as its database!!