The first time you use Housecall at: http://housecall.trendmicro.com/
Trendmicro will guide you through a series of screens they use to complete agreements with you as a user and to load an ActiveX required to enable the scan.
I does seem complex, but will get you to their very good scanner which should serve you well.
The next time you use Housecall, you will not have to go through the preliminaries, though you will have to load any updates.
I've used TrendMicro's Housecall on my own machines many times successfully, and on a wide variety of friend's and customer's machine.
That means there is a Microsoft update it did not locate.
To insure you have all critical updates run the Microsoft Winows Update….
Or check your installed updates and look for the number it applies to……