Please help me

I am using a sandisk flash disk, in that there is a antivirus avast(licenced version). while plugging in the flash drive it shows eject becasue of some malware found (Win32:Trojan-gen {UPX}), i am having nod 32(licenced version), How can i remove this virsu ? any one can help me. I cannot find any such virus using nod 32. the affected file is c:\heap32\svchost.exe, i cannot find that in my c drive also