In your case, it might be worth trying a System Restore, if it doesn't work then try the following:-
Firstly, go into Safe Mode with Networking and then switch off System Restore, you can restart this once your computer is clean. You do this because some infections hide in these restore points and reactivate themselves after you have scanned your computer.
Some people advise switching this off then back on again at the end of scanning in case something goes wrong during the scanning process and you need to restore to an earlier time. They believe that as the risk of reinfection is small and that it will only occur if System Restore is actually used in the case of something going wrong.
I disagree and always do this first and to be honest you will probably find that you are unable to restore to an earlier time anyway. If something goes wrong and you are reinfected by using it then you will have to restart the whole process again.
This is why I advise that you read up on all these programs before using them, do this and nothing should go wrong.
Make your own decision here but still get yourself into Safe Mode with Networking before the next step.
This is a list of software that will check for all the infections that are out at the minute and I would personally run them all in this order to be on the safe side.
Install, update and run malwarebytes [FREE VERSION] http://www.malwarebytes.org/mbam.php
Install, update and run smitfraudfix [FREE]
http://siri.geekstogo.com/SmitfraudFix.php
Install update and run cwshredder to check for traces of coolwebsearch infection [FREE]
http://us.trendmicro.com/us/products/personal/CWShredder/index.html
Install, update and run SUPERantispyware [FREE VERSION] http://superantispyware.com
Run this weekly to keep on top of things.
Install, update, immunize and run Search and Destroy [FREE]
http://safer-networking.org
Run this weekly to keep on top of things.
Install, update and run Ad-Aware 2008 [FREE VERSION]
http://lavasoft.com/single/trialpay.php
Although I don't really rate this software, it occasionally detects something the others miss so maybe worth using too. If you do I'd add it to the weekly scans.
Install and run both scans with ccleaner
http://ccleaner.com
Run the Cleaner scan and remove all it finds
Run the Registry scan and fix all issues but repeat this until nothing is detected.
Run this daily.
I'd also recommend Avast Home Edition if you want a good free anti-virus and remember that you can only have one or they will conflict with each other. [The list above does not contain an anti-virus]
http://www.avast.com/eng/avast_4_home.html
Even though it protects 24/7 I would still run a full scan once a month, be sure you set it correctly before scanning so that it is set on high and includes all parts of your computer including archives.
I'd recommend Comodo Firewall if you want a free firewall. Some people just use the one incorporated into Windows but this is better. http://www.personalfirewall.comodo.com/
At some stage you will find that ActiveX has been disabled in Internet Explorer. To enable go to Tools > Manage Add-ons > Enable or Disable Add-ons and when there enable it again.
You may or may not have heard this in the past, but Firefox is much better and less at risk from attack so worth checking out.
To maintain your PCs health I would do a Disc Cleanup once a month and also check to see whether you need to defragment.
A good program for removing programs that seem to refuse to go no matter what you do is http://www.revouninstaller.com/index.htm... however be careful how you use this.
If you have previously had Norton or McAfee installed on your computer you will need to use the appropriate Removal Tool to ensure that all traces of them are removed from your computer.
I couldn't post the links here as Yahoo restricts the links on an answer to 10 so I've added them to the bottom of my profile, just click on The Broom.
I would strongly suggest that you read up on all of these programs so that you are able to use them properly and benefit from their full potential.
Checking the forums and FAQ's for each is a good way to do this.
More and more people are falling for the 'pop-up trick' that says you are infected and to scan now to remove the infection. Some people press 'OK' others press 'Cancel' and others press 'X' to close the window. All of these actions can install the 'Rogue anti-virus' programs that seem to be popular at the minute. To ensure you don't infect your computer when this happens, I'd suggest you go into Windows Task Manager [ Ctrl Alt Delete ] and in the Applications tab end all the browser tasks - IE or Firefox.
Feel free to email me if I can be of further help