I know it's a very frustrating situation to be in, Jessica. My first bit of advice 
is, try not to feel overwhelmed by it all. 

This is just a guide, to get you started. If you are good at following instr., you'll 
do fine. Hopefully you'll get to the point where you can can post on a malware support 
forum, "if you need to", for further help. They'll help you step by step, but it 
may be a few days before they can get to you. 

Firstly, see if you're able to run that SmitFraudFix. If you can, print out this 
page of instr. then carefully follow the steps. 
How To Remove The Smitfraud / Generic Zlob / Quicknavigate / Virtual Maid, Self-Help

ATF Cleaner is just a very basic temp file cleaner, history and cookies. 
http://majorgeeks.com/ATF_Cleaner_d4949.html

Plus, I'd create a new temporary restore point, so you have something to fall back 
on at least. Next, see if HjiackThis will run. That would be the single, most useful, 
tool right now. That way you can post a log on their forum. If you do, let them know 
you're unable to install other programs.... that you ran SmitFraudFix and how that 
went. They'll advise you on what to do next. 
How to use HijackThis

Download for HJT and below it is a direct download for the ZIP version, so you can 
just unzip into the folder you created.... no installation. I'd create folder in 
Program Files folder for it. After you unzip HJT, rename HijackThis.ext to (any name 
you want and can remember).exe, like Jessica.exe :)
http://www.bleepingcomputer.com/files/hijackthis.php

http://download.bleepingcomputer.com/hijackthis/HiJackThis.zip

Blocking Unwanted Parasites with a Hosts File