Computer infected with trojan and is constantly rebooting. Is it too late?

Your computer can be cleaned but you will have to use a different method. If you have another computer or know someone who will do this for you it usually works. Remove your hard drive from your computer and mount it in another computer as a slave drive. You can then run their antivirus and malware removal programs to clean the drive. The problem you have is that while the windows system is running the trojan has control of it's operations. As a slave drive the system is not running and it can be scanned and cleaned. If possible use a system with Avira or Avast as I found these to work the best. Good Luck.