There really isn't anything you can do. If the e-mails are originating from your company or school, you can contact the IT administrator. In your case, what most likely happen is one of your friend's computer got infected with a worm or other malicious file. The worm harvested all contact information from your friend's address book, including your own. The worm then sent spam or other malicious files to everyone on the address book.
There some things you can do to cut down on the spam. Try MailWasher, it is a free program which stops spam before it even reaches your e-mail inbox (http://www.mailwasher.net/)
Read PC World Magazine's article entitled:
"Stop Fuming, Start Filtering Spam" -- written by Steve Bass (http://blogs.pcworld.com/tipsandtweaks/archives/003085.html)
"Last week I talked about spamming trends. From the e-mail response, it's clear you wanted more -- especially ways to fight back.
I use Eudora, the e-mail program I love to hate, and no, I'm not willing to switch to Microsoft Outlook. (At least not yet. I'll have to see what the Open Source version of Eudora looks like.)
I know what you're thinking: "Dummy, Outlook has Cloudmark, the terrific spam grabber, or the just-as-good IHateSpam."
No argument. But wait, I hear you thinking again: "What about those miraculous programs that filter your mail before it gets to your e-mail program, such as MailWasher or MailboxFilter?"
But I'm a step ahed aheadf of you now... here are a few downloads from PCWorld.com. They're either free trials or just plain free; it can't hurt to give them a shot. The first is ChoiceMail Free, Mail Snoop Pro is the next, and SpamCatcher is the third.
Quick aside: Outlook has a decent spam grabber built in. Microsoft calls it a junk e-mail filter. But it's only worth using if you keep it upgraded. Read about it at Microsoft's Office Online site and download it from Microsoft:
More Help Stopping Spam
I dug around to find articles and downloads on PCWorld.com. Don't panic. Some of these articles may look ancient (2002 is eons ago), but they're timeless, especially for those of you using older software.
* Spam Slayer: Biggest Spam Hassles Solved
* Step-By-Step: Stop the Spam--How to Filter Out Junk E-Mail
* Internet Tips: Wage War on Spam With Old Tools and New Filters..[More].