"A little learning is a Dangerous thing" ....... William Shakespeare I think sometime between 1500 and 1600 A.D
True then -- even truer today.
Sneak and scareware are both HORIBBLE and insidious tactics -- sneakware is employed hugely by sites like DRIVERMAX which offer to scan and update your drivers
-- and after its found what you think you are looking for it then informs you to that the facility you want is only available for PAID registrations.
Scareware is just as bad " Your computer *may have* a potential virus etc etc.
Any computer in the known (and probably unkown too) universe *might* have a computer virus.
Safe surfing, decent firewalls, and some proper real time AV stuff like MSE should be more than sufficient.
Please don't get suckered into these types of sites.