1 of 1 people found this helpful
First thing to do is shut him out of your computer by changing all user account passwords to something you can remember yet complicated enough to fool anyone, including that for the hidden Administrator account and for the BIOS. If that upsets family members, tough, let them get their own machines or at least make sure that none of their user accounts are Adminstrator-level ones, only regular user accounts. I would have to know what your operating system and service pack is to give instructions, if you need them. Disable the "Guest" account altogether if not already - it is normally disabled by default and should never be used as it is a vulnerability in Windows. Don't write the password you use down anywhere!
Follow the guidelines given here particularly the Safe Mode ones: Required Reading
If that doesn't help boot into "Safe Mode with Networking" by tapping F8 repeatedly while booting up and selecting that from the menu that shows up, usually the second choice. That gives you Safe Mode but with internet access, however most infections can't and wont run in that mode.
Then download, install, UPDATE (important), the FREE version of THIS software, then run a full scan, takes a while, and let it remove everything it finds, then reboot. (it will work in that mode).
Repeat with a Quick Scan in regular mode.