How can i remove status "done" from board

[Sriwan 'Wan' Khomeeklang]

We have many ticket in status "DONE" and now it still display on board.

How can i remove it. or when it disappear 

[Phill Fox]

The article at https://confluence.atlassian.com/jira/configuring-file-attachments-185729586.html tells you about how to configure where your attachments are stored. 

Assuming no changes were made on your original system you should find them in the default directory location of data/attachments subdirectory of the JIRA Home Directory.

[Nic Brough -Adaptavist-]

The attachments are all under <JIRA home>/attachments.

If you've followed the documentation, you'll have been backing that up regularly.  If you still have access to the disk on the crashed system, then it's even less of a hassle - you can simply copy the whole directory to your backup JIRA