Hi, Jenny -
Okay. The problem is with Outlook Express, and is often caused by bloated archive database files.
Try this - with Outlook Express not running, hold down the Option key when clicking on the Mail icon in IE, or when starting Outlook Express directly (by double-clicking its program icon). This will bring up a message asking if you want to compact the database files - click OK. This will create new database files containing the old data; the old database files can then be thrown away.
Something to note - when an email is downloaded in OE, it is added to the database files; when the message is deleted the database files do not shrink. This is especially bothersome when there are attachments to the email messages. If you've extracted an attachement to your desktop or elsewhere, you can then remove it from the email it came with. When you compress the database files, space won;t then be taken up by redundant copies of attachments.
Also, if you have not yet done so, increase the Preferred memory allocation for Outlook Express, and for Internet Explorer, too. Adding 20 or 30 thousand to the original Preferred amount is not excessive.
Article #18278 - Assigning More Memory to an Application