To view how much space is available for different data types, select Menu > Applications > File mgr..
To remove data you no longer need, use File manager or go to the respective application. You can remove the following:
Messages in the folders in Messaging and retrieved e-mail messages from the mailbox
Saved web pages
Applications shown in Application manager that you do not need
Installation files (.sis or .sisx) of applications you have installed. Transfer the installation files to a compatible computer.
Images and video clips in Gallery. Back up the files to a compatible computer using Nokia PC Suite.