Most easy way to reset sitecore/admin password to b is just run following script on core database.
UPDATE [aspnet_Membership] SET Password='8dC23rEIsvuttG3Np1L4hJmJAOA=', PasswordSalt='joeLPwcwMq6L7kyuVfVS7g==' WHERE UserId IN (SELECT UserId FROM [aspnet_Users] WHERE UserName = 'sitecore\Admin')
If your admin user name is different then Admin just update the “sitecore\Admin” in the above script with your admin user name.
Good read on this topic - http://www.sitecoredevelopment.com/MarkGraber/2010/June/Cannot-Login-to-Sitecore.aspx
Thanks and cheers
Just a note that this doesn’t always work if the account has been further disabled. Please see this post from 2012 which shows an updated script for also ensuring the account is enabled and approved:
http://sitecoreblog.blogspot.ca/2012/05/reset-admin-passord.html
Agree with you Jason.