alright i made a list of software i personaly use to keep my computer running in top shape, everything on the list is free. although it may ask you to upgrade to a paid version. just click on the link and download, after you download and install you should update and run a scan just to make sure you safe
Ad-Aware 2008 free - http://www.download.com/Ad-Aware-2008/3000-8022_4-10045910.html?part=dl-ad-aware&subj=dl&tag=top5&cdlPid=10844457
SpyBot SD -http://fileforum.betanews.com/download/Spybot_Search_and_Destroy/1043809773/1
AVG antivirus Free - http://www.download.com/AVG-Anti-Virus-Free-Edition/3000-2239_4-10320142.html?cdlPid=10834624
ALSO here is the link for the newest flash player that incase you havent updated yet http://www.adobe.com/products/flashplayer/