More than likely you got a trojan horse.

You can set your system by when you switch on the maching press delete key to you get a blue screen that contains your bios and it's settings and in there you should see a setting that says 'system password' or similar.

Use a 6 digit pw as that should be enough sometimes people put in a password too long and bios don't tell you it's too long and you end up having to reset bios etc.

I was hacked by someone who turned off my firewall and antivirus by rebooting my system. Are there any programs that allow you to require a password to reboot your system so that hackers can't reboot and delete your security programs. They already are password protected, but a reboot can allow them to be deleted or turned off. The guy used my email to send out mass mailings.