How to delete Attribute and Set type?

Dear all,

I created Attributes --> Set type --> and assingned it to Category for Installed base.

Now I created some installed base with the attributes.

Now i want to make changes in attributes and want to delete some attributes but system is not allowed me.

I must delete attributes becase we changed in production system and now it is very critical situation.

Pls Reply

Regards

Jayesh