I like the second resource that “The Old Computer Guy” gave you and the Bleepin Computer resource that TempoOne shared. After removing SecurityTool learn how to take control of security in your Windows 7 computer, http://windows.microsoft.com/en-US/windows7/taking-control-of-computer-security. Also, try using an anti-virus software like Microsoft Security Essentials to help you keep your system free from viruses, spyware, and other malicious software.

Good Luck!
Cassandra
Microsoft Windows Outreach

1)restart your computer and press F8. start it in safe mode
2)go on to a account your computer has RESTORE DATE setting. set it about 2 days before you got it.
3) go onto a account in normal mode, and CLICK THIS LINK:
http://download.cnet.com/Malwarebytes-Anti-Malware/3000-8022_4-10804572.html
(after the restore you will be able to search the internet on normal accounts up until the time where you would get the virus.)
4)run a malwarebytes scan and the virus will be destroyed, do a full system scan, it takes longer but will delete all and any files it has.

the logic to this:
pressing F8 is a main key point. select safe mode with your arrow keys.login. nothing will pop up hence security tool is stuck. start system restore and set it 2 days before. this means the virus hasnt yet arrived onto your computer.
you will need to restart it up to 3 times for your files on desktop to show again, but once they do go onto the internet and search for “malwarebytes download”
i suggest download.com or the malwarebytes site.
run a FULL SCAN once you have installed it. it will take longer, and even quick scan works for this virus, but full scan would clear up every virus that could be hiding between the files.
i hope this helps, the same thing happened to me. ill update each time i remember more details but thats practically what you need to do.

Scroll down to:
“Automated Removal Instructions for Security Tool using Malwarebytes’ Anti-Malware:”
Do NOT purchase any of the removal software advertised at the top of that page.

http://www.microsoft.com/security/malwareremove/default.aspx

http://windowsprotection.net/how-to-remove-security-tool-securitytool-removal-guide/

Good Luck

The Old Computer Guy