SQL2012/2008R2/2008 Express is free, allows a database of 10 gig, and is much much easier to use than CE;
CE is a very trimmed down database version that is aimed towards the old Windows handhelds.
It will not mix well with anything you've already written, the learning curve on the handicaps/limitations is very big,and it's designed more as an alternate to Access or a local file access type of database.
I would recommend that before anything else.
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