Either you have a worm, which is a kind of virus that sends itself to everyone in your inbox, or someone has pirated your email address and hidden their real one, making it appear that it is coming from you.
Download AVG free anti-virus software and run it.
Download Malwarebyte Anti-Malware software and run it. Download Lavasoft Adaware software and run it.
All of these can safely be downloaded at www.cnet.com.
If you have trouble downloading, just go to START, RUN, type in MRT and run the microsoft malicious software removal tool.
In your address book, add the following contact:
AAAAwormalert@somewhere.com
If you have a worm, it will try to send itself to the first contact in your list and you will receive a delivery failure notice to the above address. This will alert you to a security problem. If it doesn't send itself there, then you have a case of someone pirating your email address, which makes it appear to have come to you, and that's why it goes in your inbox and not your junk mail. I think this is the case because you don't know the recipients. There is not much you can do about this, except to change your email address.
Go to one of these email before it is opened, right click it and pick, show source. You will find out who it is really from and you will know what is going on. It might stop on its own after awhile because it is spammers who do this and they are always changing their email addresses to keep from getting caught.
I really hope this helps!