Greeting's

Assuming that you have already run an online scan mentioned by XTC46 and looking at your Hijackthis log I can see that your windows is patched up. And because you are still facing the problem I think you might want to give a try to Rootkit revealer
Get more information at :

http://www.sysinternals.com/ntw2k/fr...itreveal.shtml

Try using it if you find anything out of the ordinary tell us or simply post the log. Like hijackthis is used for finding adware and spyware use this for finding Rootkit's

Sience you are new in computer security field try reading this http://en.wikipedia.org/wiki/Rootkit


edit :

One more idea i can give you is running a sniffer for sometime. Try ethreal
download it from http://www.ethereal.com/

Let is run for some time, save its log BUT SAVE IT AFTER YOU SANITISE YOUR LOG'S (SEARCH FOR A TUTORIAL BY TIGER SHARK ON THIS SITE.)