This will only delete a Xat ID, not a chat.
1. Login to Xat here:
2. Enter your Xat name, password, leave protected mode set to "ON" (it's a security feature), and click the LOGIN button
3. Next window, at the very bottom of the page, look for and click on the DELETE [I]USERNAME[/I] button.
Note: You will lose everything; your account, xats, days, powers, etc...