If the banner has blocked your Internet, then go to the websites of anti-virus Dr.Web and Kaspersky from another computer. Download Kaspersky Virus Removal Tool or Dr. Web Curelt, if possible on your computer. There you can find the right code to unlock the Windows XP operating system. From the list of banners you can find one that prevents access to the Internet. Below is a list of the codes for the unlock. If nothing is found, then you need to do reinstallation of the operating system.
Take an installation disk for Windows 7 update. It must be inserted in the drive, and WE load from floppy disk. Then run the installation. Find advanced options and run them. Using "startup repair" removes all harmful programs. If you have installed Windows XP operating system, then use the recovery discs. Also perform all installation steps, you only need to select "restore". And then begins the process of returning the OS to its original state.
Use the utility AVZ, anti-malware viruses. This is a free program. Download it from the link http://www.z-oleg.com/secur/avz/download.php. Then unpack the archive. This app don't need to install, so it can be kept on a flash drive.
Run AVZ. In "search scope", select flash and disks. Right need to tick the "Carry treatment". Select a verification method. But remember that the long test will be of higher quality than fast. On the tab "search Options" apply "Advanced analysis" and "Search Keyloggers". Click "start" and wait for verification. All detected viruses will be removed. Then you need to restart your computer and scan it by antivirus program.