Now, the machines ip has changed since, download history has been cleared from both browsers.
Can you clarify this statement, is this your machine or the *******'s IP that has changed?
You might be able to find info in the Event Viewer
Under: Windows Logs - Security or Applications and Services Logs - Operational.
You may have to wait until this event happens again, only this time be more prepared.
Can you find any information from the previous ISP report that may help?
Are you wired or wireless?