If you can't find a Samsung account in "Accounts and Sync", remove the account (email address) that you used to sign up for a samsung account. This is what I had to do to fix this problem on my 2nd hand Galaxy Y DUOS that kept trying to connect to the previous owner's Gmail account.
I tried to delete his gmail account and a message popped up that I could only delete it by a factory reset. When I tried the factory reset it told me I had to delete the "Samsung account" first. I couldn't find a Samsung account anywhere so I searched and found this forum.
I followed Sasuketobi's instructions above but there was no "samsung account" to delete in "Accounts and Sync". There were just the original owner's Gmail, a new Gmail that I created and my Hotmail. By accident I discovered that it was my Hotmail address that I needed to delete - not an account called Samsung but the account I used to create the Samsung account. As soon as I deleted my Hotmail account, a message popped up saying that I had deleted the Samsung account.
I was reluctant to try the other methods on this forum.
Hope this helps someone.