While Skype displays only recent messages by default, you can view older interactions by selecting View Old Messages from the Conversations menu. Alternatively, see messages you deleted from a conversation by using a free program to read the contents of the Skype database file.
See Older Messages
To display older messages, open the Conversation menu and hover your cursor over View Old Messages. From the fly-out menu, select Yesterday, 7 Days or 30 Days, depending on how far back you want to go.
Skype can display only messages that are less than a month old. View messages sent or received over 30 days ago using a tool to read the contents of the Skype database file.
See Messages You Deleted
Removing messages in Skype hides those interactions from view but does not delete them from the program's database file.
To permanently delete messages from the database file and therefore prevent users from reading messages you deleted, open the Skype menu and select Privacy. Click the Clear History button.
Launch the application you just installed and open the main.db file located in the following directory:
Use the application's browser to locate the conversation that contains the messages you deleted.