to download HijackThis by Merijn Bellekom. Doubleclick the file, click Unzip and extract the application to C:\HijackThis. Run it from there to scan your computer.
When the scan is finished, the "Scan" button will change into a "Save Log" button. Save the log, Ctrl-A to Select All and post it here for examination. Don't fix anything yet as most of what it lists will be harmless.