DO NOT Download it. I repeat, do not download it.
It randomly pops up when you're surfing the net, even with Anti-virus on and pop-up blockers.
Just cancel it and keep canceling it.
It's a rogue virus.
It wants you to buy the software.
First of, it 'scans' your P.C. Then lets gives you some fake tip that your P.C is corrupted.
Then prompts you to buy download the software or buy it.
It's job is to manipulate your files, it corrupts them when you buy it, then repairs it. Then re-corrupts it.. Rinse and repeat.
That's what it does.
If somehow you've encountered it, go to C Drive, Program Files, find XPonline or something .
If you find it. call your computer technician. If he/she tells you it's okay, fire her/him.
If it doesn't exist, good for you.
That is all.