Windows 7: Hotfix http://support.microsoft.com/kb/974324 won't install

Hello,

I'm experiencing the problem, described here: Black and white pixels unexpectedly appear on the right side of the screen when you run Windows Media Center in full-screen mode in Windows 7 or in Windows Vista
Problem appears in various full-screen applications (games, films etc.) randomly, only in native resolution of 1920x1080. It seems to appear when most of the screen is in one color (white, black, red etc.). Those are definitely not dead pixels.
It's been going on for quite some time, I have reinstalled graphics drivers a few times since it first appeared, using DriverSweeper. It's getting worse as time goes by.
When trying to install the above hotfix, I'm presented with the "The update is not applicable to your computer" message.
I've manually installed System Update Readiness Tool (System Update Readiness Tool that fixes Windows Update problems is available for Windows 7, Windows Vista, Windows Server 2008 R2, and Windows Server 2008), which did not help - still getting the same message when trying to install the hotfix.

OS: Windows 7 x64 SP1 Home Premium
Computer Model: Dell Studio XPS 7100
Graphics: ATI Radeon HD 5870
Graphics Drivers: Catalyst Software Suite 12.6 (28.06.2012 - latest)
Aftermarket Cooler: Arctic Cooling Accelero Xtreme 5870 (the problem appeared before I replaced the cooler)
Monitor: Samsung SyncMaster B2230H
Monitor Driver: 3.0 (15.10.2009 - latest)
Display Cable: DVI
I'm using MSI Afterburner to overclock core and memory and set custom fan speeds, but the problem appeared before I started using it.

[EDIT] I was told the above hotfix does not apply to the Windows 7 SP1 because the later version of it is included in SP1.

But the problem I'm having is exactly like the one described in http://support.microsoft.com/kb/974324 - flickering black and white pixels on the right side of the screen only in 1920x1080 fullscreen mode.

Could anybody tell me what could cause this kind of artifacts?

Thank you.