To increase disk space by deleting stored newsgroup messages
On the Tools menu, click Options.
On the Advanced tab, select the options you want for maintaining the size of all message files on your computer.
To compact, delete, or remove messages from all or specific message files now, click Clean Up Now, and then follow the instructions on the screen.
Note
Most news servers periodically remove old messages. The next time you connect to a newsgroup you've cleaned up, your message file is rebuilt with just the current messages from your news server.