Appears to be Windows Vista.
I would suggest you get SpyBot Search and Destroy for spyware removal. Download here.
By any chance do you have any filesharing programs running? Limewire or bittorent? Make sure they are closed.
Perhaps you should try logging on to your wireless router to see if anyone else is connecting to your internet and to view usage statistics. Is your wireless network encrypted? If so, is it WEP or WPA? If you want to log into your router, copy and paste this into your web browser. http://192.168.1.1 Here
is a list of default passwords depending on router if you don't know what your login is.