Windows 7: partial download of attachment...a virus??

Hello guys
I have a problem in downloading attachments from my school's email which is an Outlook Web App. It gives me a partial download (check attachment of the properties of the mal-downloaded files). In the same attachment you will also find the message that I receive if I try to open the file as pdf. I am worried because I first encountered this problem when my PC was infected by Trojan programs, and my email was hacked. Though I formatted my laptop, I am still suffering from this problem. Just want to make sure it is not a virus… If not does anyone have an idea what the problem could be???
Mind that I am able to properly download the same files from Hotmail or yahoo.
Thank you