Turn on your pc then insert windows recovery CD into your cd drive turn off power. Restart your pc again. Let your pc boot from the CD. Following the given instructions. It will erase everything in your hard drive and reinstall your pc for you. Your pc will be like brand new ones. Don't use safe mode to do this! It will not work in safe mode.
After you installed, be sure update your computer security patches from uncle Bill Gate, and install anti-virus, firewall, and adware (free from Lava Soft) programs to protect your computer from further threats. Stay up-to-date or you will get more headaches. Can't stay up-to-date? switch to iMAC, no virus or patch to worry. Just need to keep up learning a whole new operating system.
Good luck.
Have great holiday season!