flash drive virus problem

I have a fash drive of 1 gb.It is infected by some troson horse, when I am connecting it to an pc it is not opening by doule clicking.when I scanned it I found infected by troson horse.I have formated it,even formated through command prompt.After that the virus is still staying in that flash drive.

give me any idea how to clean the virus.

Regards
Kishore Kumar Behera
CMS Computers Limited,Bhubaneswar
Orissa, India.