Outlook Express freezing

Is there a limit to the number of Folders that can be created under INBOX in Outlook Express 5.5 to store messages, as I find that Outlook freezes often as the machine has over 1500 folders and each folder having over 25 messages? Can this be the reason for OE 5.5 freezing? Also Word 2000 freezes when an attachment is opened. Is OE 5.5 overloaded?