The easiest way to get rid of these types of viruses is to: A) Reboot your computer in Safemode and then B) Restore your computer settings to an earlier time before the virus struck. I'm ashamed to admit how many times I've successfully used this method without a hitch. Rather than put exact instructions here I recommend that you google "How to reboot in safemode" and "How to restore settings in safemode" and find the best instructions for your operating system.
Usually with XP and many operating systems you get into safemode easily by holding or tapping F8 during the boot process. If that doesn't work you can 1) click start. 2)click run. 3)In the run window type msconfig. 4) When the System Configuration Utility opens click on the BOOT.INI tab. 5) In that window check safemode and click OK . 6) Choose Restart. The computer will reboot in safemode whereby just basic functions work and the virus can't interfere with you restoring the settings to an earlier day. Choose the basic safemode option when prompted. It's all you need. Then choose the option to restore your computer to an earlier time and follow the prompts. If you used the Sytem Utility Configuration method to get into safemode then you may upon your next startup have to go back into that utility and undo the safemode boot process by checking normal.
I've seen all kinds of advice about deleting infected registry and dll files but that's way to complicated and usually ineffectual and you don't need to buy a program to fix the problem. I sometimes wonder if some of the people offering advice regarding these types of problems aren't subject to a conflict of interest. These types of viruses aren't designed to malisciously vandalize your computer. They're designed to get info or money from you and therefore they aren't as bad as some.