i work for an Internet company.

Actually those emails are a type of spam. These emails multplies itself!! These programs are intelligent enough that it takes addresses from your address book and sends it to them including yourself. Some of them contains virus, some are just ads or scam attachment.
Meron na ngang viruses embedded sa mga .doc or .jpg file attachments eh.

Doublea is correct, dont open email attachment with .exe file from suspicious mails, its like opening a can of worms