XP?
1.- Open CONTROL PANEL
2.- Double click NETWORK CONNECTIONS
3.- highlight "Local Area Connection" Right click and select Properties, a window opens, highlight Internet Protocol, click properties button, another window opens. tick the radio button at the top "Obtain an IP address automatically", click OK, OK
4.- If you are using Wireless, you will need to highlight "Wireless Network Connection" instead of Local Area Connection.
The problem may return, download this software, install, update twice, Perform Full Scan
Use the Free version
http://www.malwarebytes.org/mbam.php