Since I am a teen and i have 16-year old sister which clicks on every link possible and downloads everything from p2p networks,I can help you.
Choose selective startup
Go to the startup tab and disable everything that is not needed,if you arent sure what to disable post a screenshot here and
I will try and help.
2.Press CTRL+ALT+DELETE and go to processes tab.
Check the processes on > http://www.sysinfo.org/startuplist.php http://www.processlibrary.com/ http://castlecops.com/StartupList.html
If any of them are viruses,find out how to delete them.
Install Firewall,AntiVirus, and AntiSpyware softwares and scan for viruses and spyware.
Install CMCleaner or CCcleaner and scan.
Pay attention to registry.
5.Install HijackThis and post the log.
Block porn sites and all the sites which are known to contain viruses.
Block sites that contain words hacking,cracking,writing viruses and that kind because teens are wannabe hackers and
most of them don't know what they are doing.
Block sites that contain words like free smileys,cool msn stuff,cool programs because most of them are malicious.
Uninstall any theme changing program,they take very much resources.
Disable all visual effects,it makes computer very fast (disable the XP theme too).
Uninstall any toolbars,smiley packs and MSN addons.
Uninstall any P2P program.
Defragment (could take hours)
Block any unwanted content.
Scan each week at least once
Use XP tweaks to improve performance
Block MySpace (You don't want them to get all kind of malware from that site,and get drugs from it)
Install monitoring program which will record what they do.
Restart and run msconfig again,then see if everything is ok.
Trust me,that isn't enough
EDIT> I found this while surfing trough boards,should help youhttp://www.bleepingcomputer.com/forums/t/44694/slow-computer/http://www.bleepingcomputer.com/forums/t/2520/how-did-i-get-infected/
Soon I will do a clean-up on my schools worst conditioned computer (my teacher asked me to do this) and it is used by teens so I will be able to provide you more information.
Edited by eXpelled, 22 September 2007 - 10:18 AM.