What you've got is the latest scam on the net, scareware. It's a false message trying to trick you into paying for a rogue program which is the source of the message.
More info >
http://news.bbc.co.uk/1/hi/technology/7955358.stm
and this link >
http://www.scmagazineus.com/Microsoft-report-shows-scareware-file-fomat-bugs-on-rise/article/130399/
Long story short, viruses are no longer a some teenage geek getting ego kicks out of writing some script. It's all about Identity Theft, and this type of threat which makes the authors money. Same way Nigerian email scams and email marketing to buy Viagra etc. It's all about the money.
Unfortunately if you're using Windows it's getting worse, although it pains me to say that. Apple and Linux users are pretty much in the clear.
You can't legislate for this, the best Anti Virus and Fireswall protection will not help. The scareware authors are quite cunning and crafty in the manner they deliver this software onto a users PC and more often than not using Peer to Peer or searching the net for dodgy content will guarantee this kind of thing.
I see this virus at leat 5 times a day, every day at work. Most of the time I can kill it. However it mutates almost daily. At the moment it's deadly and I've got to format 3 machienes later on today which I hate to do as it's conceding defeat . It's generally a bitch to kill and the latest version of this is in the form of Rootkits which are essentially invisible to the Windows API (application programming interface), in other words even taking the hard disk out and scanning it in a clean machine wont do anygood as Windows just wont see it. Then I use a Linux box to sort it.
Anyway enough techno bollocks. What you can try is this;
Download and run combo fix <a class="postlink" href="http://www.bleepingcomputer.com/combofix/how-to-use-combofix" onclick="window.open(this.href);return false;">http://www.bleepingcomputer.com/combofi ... e-combofix</a>
Download and run Spybot > <a class="postlink" href="http://www.safer-networking.org/en/download/index.html" onclick="window.open(this.href);return false;">http://www.safer-networking.org/en/download/index.html</a>
Download and run BHO Daemon > <a class="postlink" href="http://majorgeeks.com/download3550.html" onclick="window.open(this.href);return false;">http://majorgeeks.com/download3550.html</a> (post what it finds and I'll take a look then advise)
Download and run Hijack This > <a class="postlink" href="http://majorgeeks.com/download3155.html" onclick="window.open(this.href);return false;">http://majorgeeks.com/download3155.html</a> (you'll need to do a scan , save the log into a text file and pm me the log, I'll look and advise)
If you try any of the programs and they will not run then the Rootkit is blocking them. You can try downloading AVG (not the free version but the Pro version on a 30 day trial and run the rootkit component). Sometimes if that fails then that is when you need a Linux box or BartPE to update registry permissions which are being denied, and to manually delete around 7 dll files with the uacxxxxxxx.dll id (random generated numbers and letters after uac). Dont go mad and search for uac and delete as this is a legit Vista App and NOT to be confused, the other two files are .dat and .sys
Empty all Temp Files and Folders
Use the Folder view option to show all hidden files, and to show protected Operating System Files. When you do that empty all Temp Files. For XP Look in Documents and Settings\what ever the user name is\Local Settings\Temp
also Documents and Settings\username\Temporary Internet Files - DO THIS FOR EVERY USER
look in WINDOWS\Temp
If you want to free up space at the same time delete all files showing in blue , starting with the letters KB at the beginning of the file name - these are redundant updates files and can grow over time. Check the C\Windows\inst folder, anything in there can go as well.
For Vista; C:\Users\Owner\AppData\Local\Microsoft\Windows\Temporary Internet Files
also do the C:\Users\Owner\AppData\Local\Temp Folder
If all that is too much, and you have a legit Windows, all your softwarea and data files backed up, and 24hrs spare over bank holiday to setup you pc again just format the thing and start again!