Salesforce.com has an out of box way to merge two accounts. You can find it by clicking the Account tab and then clicking Merge Accounts. But nobody ever remembers to go there, if you even notice it, so we made it easy to find. The Find Duplicates button goes right on the Account page, so a duplicate search is only one click away.
Click on the Find Duplicates button from any account to find related accounts.
Then use the Salesforce merge tool to merge any duplicates you find.