HELP!! I cant go to any website cuz I keep getting this: Internet Security Threat download Antivirus

Your computer is infected with rogue software called antivirus 2009. Download and run rogue antispyware removal tool from http://www.spywaregeeks.com to remove the rogue software from the computer.

This sounds like spyware was installed on your computer. When this happens it affects how your web browser behaves. The affects can range from directing you to other sites to stealing information entered on other web pages. What you need to do now is remove it, but since you cannot go anywhere else besides yahoo, you need to get on an another computer and download a spyware remover. You would then save this to a disc (cd or dvd) or a flash drive. Install it and remove the spyware. Or you could always purchase one from a local computer/electronic store. Two softwares that I can personally vouch for that target spyware are: Spybot -Search and Destroy (free and will do the job no problem, but lacks measure to prevent more spyware from occurring, the download link is in the source) and Spysweeper (not free, but often renowned as the best anti-spyware software and offers better preventative measure in avoiding spyware, it is available to download (in source) or purchase at your local computer store.) If you want what I am using then I would recommend AVG Anti-virus (download link in the source), which is a free software that protects and prevents virus and spyware. So far I have had no problems. Lastly, you need to be responsible about what kind of websites you visit. This includes: Don't click ads, research products through google/yahoo searches, don't install anything unless you know what it is and what it does, and always download anything directly from the company/source. Following these tips will help you avoid any virus and spyware from malicious sites. Should you have anymore issues, please provide additional information and I will be happy to help.