how can I format a CDRW cd to use again?

how can I format a CDRW cd to use again?

You dont want to "format" it. When your burning the CD bring in sure that the disk doesn't finalize. Usually its a checkbox. Next time u want to use it again simply erase the disk with nero or w/e ur using and afterwards burn again.
put it in the drive, progress to my computer , right click the drive and format disk
right click it select full format and set there for 20 minutes.
i own nero software and with it it give me the option to erase and work fine, you might see if you can download a free trial variation of nero! good luck!!!