let's say a virus infect the file , it is duplicate the file and rename it to .exe .

i always found out when the antivirus scanner is running , it will detect the virus and the virus seems to be infected on those .exe file name .
for example , i got IMISSYOU.jpg , but when the scanner is running , it will detect the IMISSYOU.jpg as uninfected , but IMISSYOU.exe as infected .

2nd question is , usually virus will appear in a thumbdrive as hidden file ?

Erm.

1. it binds itself to the host file (*.mp3, image files... etc) CMIIW
2. Not really, look at "Macromedia Flash" Flash Drive infection

Mind me saying a bit, but I think the TS might be talking about the virus creating a second file with ALMOST the same filename as the Image name, except the extension is for an executable. i have seen these types of viruses before. Just delete the "created" virus and corresponding infected files.

Cheers!

If that's the case, yea, like brontok, just delete that executable file. haha

Cheers