Why did my facebook account send a message to everybody on my list from me? Virus?

[Darren0901]

Download, install and run CCleaner to clean up old temp files.
http://www.ccleaner.com [Free]

Restart your PC in safe mode with networking
http://www.pchell.com/support/safemode.shtml

Download, install and run a full scan with Malwarebytes
http://www.malwarebytes.org

Run a full scan with Micro Trend House Call
http://housecall.trendmicro.com/

After the scans, restart the PC and update your anti-virus, remember to only have one anti-virus installed on your PC
http://www.avast.com/eng/download-avast-home.html [Free, if you do not have one]