If after downloading the file from the Internet, the computer is automatically rebooted, most likely, was infected. It remains only to understand what area attacked by virus. Often it manifests itself in the form of a banner of a pornographic nature containing information about the impossibility to use these or other capabilities of a PC. For example, malware can block access to the Internet or the operating system to crash the browser or take over your account on some sites. When the computer starts, programs or attempt to log in to your personal account, as a rule, a pop-up window with a warning about the impossibility of the transactions and the requirement to send SMS to short number, in order to restore access.
Do not send SMS, since the malware and shortcode not interrelated. It's a trap, which slammed shut immediately after debiting the account of the phone. Of course, and no unlock code in the answer you get. Therefore, in any case, banner will have to go other ways.
Try to guess the password by rebooting the computer and turning it on in safe mode. This can be done at special sites, for example, http://sms.kaspersky.ru/ or https://www.drweb.com/xperf/unlocker/. If after several entries of code positive result was not achieved, then leave this idea and use other methods.
To get rid of the banner, blocking access to the Internet or not being able to log in to your account, clean the Hosts file located in Windows/system32/drivers/etc/hosts. Open it with Notepad, delete everything below line 127.0.0.1 localhost, then save the changes, scan the computer with antivirus and restart the car.
If the banner could not get rid of, then download the utility http://support.kaspersky.ru/viruses/avptool2010?level=2 or http://www.freedrweb.com/cureit/ to a flash drive and use it to scan all files. The scan time, typically at least 2 hours, depending on the size of used memory and CPU power. But this method is the most reliable of all these and allows in each case to resolve the issue.