can not delete a .dll file that is a trojan

Welcome to Majorgeeks!

You post is not very useful to us.

• You did not specify what the infections is called
• You did not give us the name of the file
• and you did not say where the file is located.
• you did not tell us what version of Windows you are running (which leads to my next question).
• Is it in a system restorer folder? You cannot delete files in system restore without disabling system restore.

Try running a scan with Symantec AV in safe mode.