Digital Signature Expiration - Company Out Of Business

Unfortunately in this economic climate, too many businesses are closing up shop. With this said, the software I currently uses pushes reports out in Excel 2003 that are digitally signed. As the company has gone out of business, is there a way to resign the reports? I do not have the original key to take their digital signature off, but I have purchased my own digital signature. Can someone please explain the best course of action or any suggestions as to what I should do?

THANKS!