I want to register a domain that you show as expired, but it says domain not available.
Expired domains are retained during the grace period for the previous registrant to renew. During that time, only the previous registrant has access to renew that name.
You can wait for the domain to drop out of all grace periods and redemption periods, and buy it regularly right when it goes back on the general availability market. For time-frames on when a domain will be in general availability again, you can refer to this article, "What Happens When a Domain Expires".
You also may be able to place a back-order on the domain by utilizing our auction partner, NameJet. Use either the Pre-Release Auction program or the Pending Delete service in an attempt to get expired domains.