See if you can select into another table: select * into newtable from oldtable
If that is not possible, and you do not have a good backup, and you have COMPLETELY RUN OUT OF ANY OTHER OPTIONS, then you can run DBCC CHECKTABLE (tablename, REPAIR_ALLOW_DATA_LOSS) http://technet.microsoft.com/en-us/library/ms174338(v=sql.110).aspx
WARNING!!!! If you run DBCC CHECKTABLE with the REPAIR_ALLOW_DATA_LOSS, there is a very high probability that you WILL LOSE DATA. Also, there is no guarantee that DBCC CHECKTABLE (tablename, REPAIR_ALLOW_DATA_LOSS) will be able to repair the corruption.
BEFORE attempting ANY repair, shut down SQL Server and copy the .mdf and .ldf files off to a safe place, so you can always get back to your starting point.