This page explains how to handle the scenario where you get an error while creating AdSense account saying your email address is associated with another AdSense account.
Google allows anyone to create only one personal AdSense account. In case of India, only one AdSense account is allowed per address.
If there is already an AdSense account associated with your email address, you will get this error when you attempt to create an AdSense account through this site:
"It appears that the email address you specified is currently assosciated with a Google AdSense account. You cannot create another AdSense account using this email address."
This error means you already own an AdSense account and so you cannot create another account. It is possible that you created an AdSense account in the past but you forgot about it.
To use this existing account, go to http://www.google.com/adsense and try to login using that email address and your password.
If you do not know the password, try to recover the password.
Try to login to your email account and check if there are any emails from Google regarding AdSense.
If you are able to successfully login to your AdSense account in the Google website, it means it is a valid AdSense account. You can associate the valid AdSense account to this site through the Associate AdSense Account option.
If none of the above options work and you are not able to login to AdSense account or if you believe you never created AdSense account, then your next option is to contact Google. It is possible that someone else accidentally used your email address and attempted to create an AdSense account. In that case, you can request Google to remove the AdSense account associated with the email address.
You may post the details to the AdSense Forum and request for help.
If you do not get any help from the AdSense Forum, then your next option is to use another email address and try to create an AdSense account.