There's a piece of supposed security software doing the rounds called Security Essentials 2010.
This is an infected piece of malware and should NOT be downloaded or installed.
It normally arrives by way of an email informing you that you have a virus, and to clean your system you need to download and install Security essentials 2010. It can also appears as a pop-up on a web page.
This is not to be confused with the excellent Microsoft Security Essentials, which absolutely should be downloaded and installed (for Windows)
More details: (notice the inconsistent lower case 'e', but by this time, it's probably too late!)
Known System Changes:
%StartMenu%\Security essentials 2010.lnk
%Desktop%\Security essentials 2010.lnk
Value: Security essentials 2010
Data: C:\Program Files\Securityessentials2010\SE2010.exe
Delete Security essentials 2010 files:%Program Files%\Securityessentials2010\SE2010.exe
Delete Security essentials 2010 registry entries:
HKEY_CURRENT_USER\Software\Security essentials 2010
HKEY_LOCAL_MACHINE\SOFTWARE\Security essentials 2010
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run “Security essentials 2010″
Sadly, if you do get yourself infected, the absolute safest and best way to rid your system is to completely re-format your hard drive and re-install Windows from fresh. A pain, but pretty much the only guaranteed way to safely remove all malware (some of which will have hooked itself so deep to your OS that you won't even know it exists).
This is why it is ESSENTIAL to have a current and viable backup system in place.