This is obviously not the virus name, simply the file that contained it. When avast identifies a virus it gives you a virus name, its location and filename that the virus was found in.

Without the virus name it is often imposible to identify the virus from the infected filename as many of these filenames are randomly generated in an attempt to combat weak AV programs looking for filenames.

However, in this case, your search was not very effective, I found lots for fsg_4104.exe, a simple search on google returned 636 hits. The first being http://www.liutilities.com/products/wintaskspro/processlibrary/fsg_4104/

WinTasks Process Library

fsg_4104 - fsg_4104.exe - Process Information

Process File: fsg_4104 or fsg_4104.exe
Process Name: Trickler
Description: Application that is associated with the file sharing software iMesh. The application has many versions.
Company: The Gator Corporation
System Process: No
Security Risk ( Virus/Trojan/Worm/Adware/Spyware ): Yes
Common Errors: N/A

It would appear to some sort of trojan, adware or spyware associated with Gator, monitoring your internet activity and then reporting home.

HTH David