The flash tool for Xperia™ is actually called Emma, and today it runs on all Windows computers, with a few exceptions*. This tool is confirmed working for most markets globally**, with a few exceptions*** due to distribution restrictions.
Download and install the tool here.
To learn how to flash software on your phone, please see the How to use the flash tool page.
* From Thursday, 6 July 2017 Emma will not function on Windows Vista.
** Afghanistan, Albania, Algeria, Andorra, Angola, Anguilla, Antigua & Barbuda, Argentina, Armenia, Aruba, Australia, Austria, Azerbaijan, Bahamas, Bahrain, Bangladesh, Barbados, Belarus, Belgium, Belize, Benin, Bermuda, Bhutan, Bolivia, Bosnia and Herzegovina, Botswana, Brazil, British Virgin Islands, Brunei, Bulgaria, Burkina Faso, Burundi, Cameroon, Cambodia, Canada, Cape Verde, Cayman Islands, Central African Republic, Chad, Chile, Colombia, Comoros, Congo (Democratic Republic of the), Congo (Republic of the), Costa Rica, Cote d’Ivoire, Croatia, Curacao, Cyprus, Czech Republic, Denmark, Djibouti, Dominican Republic, Ecuador, Egypt, El Salvador, Equatorial Guinea, Eritrea, Estonia, Ethiopia, Fiji, Finland, France (including Guadeloupe), French Guiana, Gabon, Georgia, Germany, Ghana, Greece, Grenada, Guatemala, Guinea Bissau, Guyana, Haiti, Honduras, Hong Kong, Hungary, Iceland, India, Indonesia, Iraq, Ireland, Israel, Italy, Jamaica, Japan, Jordan, Kazakhstan, Kenya, Kosovo, Kuwait, Kyrgyzstan, Laos, Latvia, Lebanon, Lesotho, Liberia, Libya, Liechtenstein, Lithuania, Luxembourg, Macau, Macedonia, Madagascar, Malawi, Malaysia, Maldives, Mali, Malta, Martinique, Mauritania, Mauritius, Mexico, Moldova, Mongolia, Monaco, Montenegro, Morocco, Mozambique, Namibia, Nepal, Netherland Antilles, Netherlands (including Bonaire), New Zealand, Nicaragua, Niger, Nigeria, Norway, Oman, Pakistan, Palestine, Panama, Papua New Guinea, Paraguay, Peru, Philippines, Poland, Portugal, Qatar, Reunion, Romania, Russia, Rwanda, Samoa, San Marino, Saudi Arabia, Senegal, Serbia, Sierra Leone, Singapore, Slovakia, Slovenia, Somalia, South Africa, South Korea, South Sudan, Spain, Sri Lanka, St. Kitts & Nevis, St. Lucia, St. Vincent & the Grenadines, Suriname, Swaziland, Sweden, Switzerland, Taiwan, Tajikistan, Tanzania, Thailand, Togo, Tonga, Trinidad Tobago, Tunisia, Turkey, Turkmenistan, Turks & Caicos, UAE, Uganda, Ukraine, United Kingdom, United States, Uruguay, Uzbekistan, Vanuatu, Vatican City, Venezuela, Vietnam, Western Sahara, Yemen, Zambia, Zimbabwe.
*** China, North Korea, Iran, Burma, Cuba, Sudan and Syria.