Someone used my email to send dodgy stuff to one of my contacts

macman

So install one of those AV's, run a full scan, change all your online passwords on another PC and don't use any of the affected accounts until you're confident you are clean.

The_Grandmaster

The order to run things in my opinion is:

Download Malwarebytes Anti-Malware 1.46 - FileHippo.com Download and Install malwarebytes. Go to UPDATE tab at top, then click CHECK FOR UPDATES. Then run a QUICK SCAN. Once finished, remove anything it finds and post log here.

Then go to UPDATE tab again, click CHECK FOR UPDATES, then run a FULL SCAN. (Going straight into full scan may take a longer time if there is malware already which can be removed with the quick scan). Remove everything it finds and post log here.

Then download and install: Download HijackThis 2.0.4 - FileHippo.com
Click on the top button in the program which will make a log within seconds.

If you do have AVG on the computer, first remove it via the control panel, then remove anything left with: http://www.avg.com/download-tools

Then Avira AntiVir Personal - FREE Antivirus Install, update definitions and run a full scan. Remove everything found and post a log here.

Now change the password/remove the e-mail account.