What to do about signing a contract?

You don't specify what type of work you have done for the company, but generally they can't force you to give something that they did not contract for.  If the contract you did sign did not specifically make your work product their work product, then they will have a hard time enforcing a return (especially if they have since voided the contract).    If the contract did have a provision that everything you had done up to the signed became their exclusive property (intellectual or otherwise), then they may have a leg to stand on-- an you should return the work.  If you are not sure what the wording on your contract means, you may want to arrange a quick consulation with an employment law or intellectual property law attorney to review the document so that you will know for sure what your liabilities are.  A review of a contract shouldn't take more than an hour and run from $100-300 depending on the attorney that you work with.  This is a bit steep, but it's still a small price for peace of mind.  If you are an independent contract, you may also want to have the same attorney draft you an agreement that you can use with future clients to avoid this confusion next time.

Even if the contract does not favor your employer because it fails to set out who was the owner of your work product and there are no other employment or contractual documents regarding your work prior to the contract, then you still want to consider your refusal carefully.  As part of your consideration, make sure that they have not filed any copyright or patent rights to your work.  If they have, you are going to need to take some additional steps before you can use the work without a lawsuit hitting you.  You need to file a suit to clear up who is actually the owner of the copyright or patent.  Also think about the industry that you are in.  Some industries are small enough that an event like this could discourage the next potential client or employer from wanting you on a project.  To resolve the issue, you may want to make an agreement to give them a copy of what you have done in exchange for a positive or neutral future reference. Essentially, make an agreement to dissolve the relationship amicably.  This is only if your in an industry where negative vibes can haunt you.  Even though you have legal remedies, sometimes the best option is a business remedy that serves your long-term business needs.