If you are using AOL Instant Messenger (AIM), it is possible that every chat you participate in is being recorded and saved on your computer. Depending on how your settings are configured, you could be saving all of your instant messenger conversations, all of your AOL chat conversations or both. To delete your AOL IM history, you can perform the following steps:

1) Open AOL Instant Messenger
2) From the Edit menu, select Settings…