Trojan.Win32.Starfield is a malicious software, new form of Trojan.Win32 or Trojan.Win32.agent.akk, introduced by a rogue anti-spyware. It installs without user permission and shows fake critical error messages:

Critical System Error!
Your computer was infected by Trojan.Win32.Starfield
It’s dangerous for your system, some files can be lost and your browser can be slow!
Click OK to download the antispyware program to clean your computer!

or

Error!
Your browser was hijacked! Some results was changed by porn advertising!
You need to clean your system immediately to prevent it.
Download the newest antispyware software!

Trojan.Win32.Starfield is not a virus, but it is a part of rogue anti-spyware software. It may come with fake video codecs when you try to view adult movies. Trojan.Win32.Starfield also known as Win32/StarField.B!Trojan or Trojan.Win32.Startpage.fq.

Source: http://www.spywares-remove.com/trojanwin32starfield