You can get HijackThis from here:
http://www.daniweb.com/techtalkforums/thread18768.html
To use hijackthis, unzip it into it's own permanent folder before fixing anything with it so that the backups it creates cannot be deleted accidentally (not a temporary folder, directly on the drive, or directly on the desktop -- in a folder on the desktop is fine).
Example:
Click My Computer, then C:\
In the menu bar, click File, New, Folder
That will create a folder named New Folder, which you can rename to "HJT" or "HijackThis." Now you have C:\HJT\ folder; put your HijackThis.exe there.
To use hijackthis, close all browser windows, double-click on hijackthis.exe, select Do a system scan and save a log file. The scan should only take a few moments then a window will pop up to let you name the file to save (or you can just leave the default). After you hit OK, the saved log will open up; copy the entire contents of the log and paste it into the Quick Reply box here.