Genuine Windows Validation problem

Hi,
I think I have a virus as I have all of a sudden had a notification saying that my windows is not genuine, I bought my desktop Medion Computer from Lidl about 8 years ago with all the software. In the right hand corner at the bottom there is now an icon that says ´you may be a victim of software counterfeiting´ when I hover over it. Ive run Malware bytes and its picked up nothing, Ive got avast anti virus and tried to restore the system back to last week and then run the malware bytes, but its still there. Ive looked on google and there are some links that say that its a trojon virus, but I wondered if anyone had any experience of it or of how to get rid of it.
Many thanks

You do not say which version of Windows, but from the age of the machine, I would guess XP or Vista.

Windows validation errors are not always a virus. sometimes Microsoft update their software, and falsely reject perfectly valid licence keys. The other reason for failing validation can be if you have made any changes to the machine.

Windows validation works by taking a snapshot of the machine and generating a code. If you make changes to the machine, e.g. change the hard disk or other components, it can invalid this snapshot, and Windows needs to revalidate. Has anything been changed.

Hi Alan, many thanks for your help, sorry Ive not been able to get onto my computer as it wouldnt allow me to get passed putting the password in.
As much as I know, Ive not changed anything on my computer and you are correct, its windows xp im running.
The reason Im back into my computer is because this time, I clicked on the pop up about not having a windows genuine copy and it let me in, then gave me a file to download...WGAPluginInstall.exe.
Now its saying that the plug in has failed and to check in firefox files to see if two files are there. One of them is, the other isnt. Ive tried to run the file again...twice and still no luck.
Not sure what Im doing or what I should do for the best now, any suggestions?

set internet explorer as your default browser then try downloading the file again. And try running windows update -even though xp is now unsupported it should let you download the updated WGA file you need.
However, in reality you need to get rid of that PC. Windows XP is a major liability now

Hi Jon, thanks for the info, I took what you said and instead, tried to reset firefox. Anyway, it worked and although my computer is really slow to start up now, the windows validation pop up has gone yey. Thinking of getting a new laptop with uptodate os on, as that gave me a bit of a fright. Thanks again.