Sillyman,
I have seen just about every way into a computer, either by hacking, sniffing, surfing, social engineering, etc...
what you are describing, does not sound like anything that I have heard.
I have extensive training in computer security and computer forensics....
however, to give you the benefit of the doubt...
here is my perscription, if you will to help you out.
1) update you antivirus software and run a full scan of your system.
if you do not have a antivirus program... go to AVG Anti Virus by Grisoft and download this very good free anti virus program.
100% detection rate of AVG Anti-Virus System is continuously certified by independent ICSA laboratories
2) use a software firewall... if you don't have one.. download the free version of Zonealarm from:
Zonealarm
The award-winning personal firewall automatically blocks dangerous Internet threats - known and unknown - guarding your PC from hackers and data thieves. ZoneAlarm provides the basic protection individuals need to secure their PC and keep their valuable information private.
this will prevent anyone from accessing your computer.
3) go to Ad-Aware or Surfin Guard Pro by Finjan
and down load SurfinGuardŽ Pro 5.7 - Beta.
SurfinGuardŽ Pro protects PC users from new, unknown Internet threats by monitoring and containing the behavior of downloaded progams and active content. SurfinGuard Pro runs active content (e.g., executables, ActiveX, scripts, Windows scripting files and Java) in a protected "sandbox" called the Safe Zone that automatically blocks potentially hostile actions.
5) go to Swat-it by Lockdown Corp
download a program called Swat-it. It will remove trojans and bots.
Swat It is a Completely FREE program that scans your files for Trojans, Worms, Bots and other Hacker programs. Swat It can detect and remove over 3000 different Trojan programs plus variants.
6) go to: TDS Trojan Finder by diamond cs TDS. It is a trial for a Trojan finder and removal tool.
The worlds most comprehensive anti-trojan system just got even better!
There are several anti-trojan systems in existance, but none can even be compared to TDS.
Now, I can suggest several other programs, as Jim Beau suggested, Spy Bot S&D is a very good program.
Using a combination of these programs or all of them will keep your computer safe from hackers.
I use them and several others... as well as test out many new programs that come on the market.
The above programs all work well together, and well with Windows XP.
Good luck and let me know how you make out...
Tank863