Hi Emily, welcome to DaniWeb :D
Be sure your system is set to "Show hidden files and folders"
Get the Pocket Killbox from here:
http://bleepingcomputer.com/files/spyware/KillBox.zip
Unzip the file to your desktop.
Go offline until this is completed (you may wish to print these instructions).
Boot into Safe Mode and do a search for these files and delete any instances found:
param32.dll
guninst.exe
popup_bl.dll
systr.dll
svrhost.exe
If any could not be deleted, (most likely param32.dll), run Pocket Killbox and paste the full file path of file in the box and click on Delete on Reboot. Click on the button with the red circle and an X in the middle; you will get a message saying File will be deleted on next reboot, Process and Reboot now?, Click Yes to reboot. (Note: the 'file path' will be something like C:\WINDOWS\System32\param32.dll)
Do you have "smitfraud.reg" on your desktop?
Close any open browser windows, scan with hijackthis, and post a new log please.