Surf safe! If you want to stay away from malware (trojans, spyware, adware...), which can become very annoying (popups) and even block or redirect certain popular sites, we recommend using the following free programs.
SpyBot S. & D. can detect and remove a huge variety of threats from your system. Additionally it can apply some sort of immunization to internet explorer that will make your computer harder to infect or hack. Spybot will sometimes solve a common problem with infected computers and flash videos where you could not see the video player on some sites you visit. However, If the problem remains, you are facing a common bug with flash, not an infection.
Download Spybot - Search & Destroy
Adaware can scan your entire computer for adware/spyware and offer you to delete or quarantine them. The free version is strictly a scanning program, it doesn't offer real-time protection. It is a good complement to Spybot in our opinion. Note that this product is endorsed by Google.
Download Adaware
Additional tips for Windows users
Windows Update should be used frequently, if not set to run automatically, so that your system remains up to date. You can find it at http://windowsupdate.microsoft.com/. Note that this page only works with Internet Explorer, however, we would recommend using:
Firefox is safer and faster than IE. Many attacks will not work against you if you are browsing the web through firefox. Additionally, you will find that our popular toolbar will be more efficient in Mozilla Firefox.
Windows Defender in Windows Vista and can sometimes detect a threat. We recommend scanning your computer with it if you think something is still wrong with your computer even after running Spybot and Adaware. You can launch it from your control panel > security page.