First of all let me say to you that you were a victim of social engineering. Unfortunately this happens a lot. Hopefully when other read this, they will know what to do. The message you got was a popup that looks like an actual online virus scan company, and tricks you into thinking you have a virus. So you try to fix it by clicking the link, and once you do, then the virsu or trojan gets installed and then you start having problems.
An easy fix with Windows XP, Vista, or Windows 7 is to use the system restore feature and restore your system to a date before you got the virus. After you computer is back up, then immediately install an anti-virus program and let it scan your computer. If at all possible, this should be done disconnected from the internet, but sometimes you may need to if the anti-virus program needs to download updates.
Here is a good link on how to do a system restore with Windows Vista or Windows 7:
www.howtogeek.com/howto/windows-vista/us...ista-system-restore/