If you got the WAT update it will screw up activation but can be fixed so check if you installed it with update history in control panel
If determined to be pirated, MS will put your system in notification mode, however it will still boot, and function. You just get a nag screen at boot. Much like using WinRAR after 30 days. You will not get the symptoms discribed in this post. Given the user got a blank screen AND A MOUSE POINTER means it got to at least the GUI portion of the boot sequence, meaning it should have nothing to do with boot loader problems.
I just Installed that KB971033 update. Noticed that upon reboot that it was gonna hang at the blank screen with the mouse pointer. It stayed there for about 3 to 5 seconds then the welcome screen appeared. Prior to that update it would boot right to the welcome screen. So I think I just doomed my machine again.
As said by many on this forum, all loaders may be successful in neutralising kb971033 but why take a chance. As of now, is there any benefit except to Microsoft?. Installing that update helps MS to check the state of the game, while bringing no benefit at all to me. Would be different (perhaps later or perhaps not) if installing that update was required to install all other updates (like in XP). This is not the situation now so why install at all?
WinFLP is right a loader would not cause the symptoms you described. could have been missing or corrupt windows boot files