UNABL;E TO ATTACH FILES TO E-MAIL IN OUTLOOK

Hello,
I am running XP and using Outlook for my calendar, e-mail, and contacts. When i click on the drop down to attach a file to an e-mail, the drop down diappears but does not open and the e-mail's status on the Task Master is, "NOT RESPONDING." The new e-mail must be cancelled to continue on.