You have two partitions now.
The boot camp software cannot always restore to one partition.
If your Mac partition is too full, or if you have had any directory problems requiring repair by other disk repair utilites, such as Disk Warrior, then you are fixed. Disk Warrior is very good at fixing directory problems, but often prevents Boot Camp from removing the _other_ partition when you want to.
If you tried some disk repairs from Windows, or did not originally use Boot Camp to make the Windows partition, then you may be out of luck.
Your choice then will be to erase your drive, and you will lose everything. Backup first....