Virustotal.com

  At times anti-virus software reports that a file is or could be a virus.This uncertainity is difficult to clear.
  Now the usual thing that is done is to seek an opinion from others before doing anything.There is a similar online solution too.Similar in the sense that you've the opportunity to test the file using multiple anti-virus software and then decide what to do.
  This is the service offered by virustotal.com.The file to be tested can be uploaded directly(in this case max. file size is 10 mb) or sent by email(max. file size is 20 mb).For sending the file by email the address should be scan@virustotal.com and the subject is scan.
  After a few minutes the detailed results are displayed:either a link is provided or an email is sent.I sent a file by email and this is the result:

The best part is that this is a free service accessible by all.