Without knowing more about the structure and what exactly is performing badly, it's going to be very hard to suggest solutions. Is the performance bad on inserts or on reads? If on reads, have you examined the execution plans to ensure that your indexes are being properly used? Are you maintaining the indexes and statistics?

If on inserts, it sounds like you might need to come up with a more normalized storage mechanism. That's a big topic. Again, it will be hard to advise you on what to do precisely in a post on a news group especially without adequate information. I would suggest getting more knowledgeable on general database design. Check out an old book, Handbook of Relational Database Design by Fleming and von Halle. That should move you in the right direction.

If you need more help, you'll need to post specifics. What is the existing structure? Where are your performance bottlenecks? That sort of thing.