TFT screens have thousands of pixels, on a 1024x768 monitor, there are three cells for each pixel - one each for red, green, and blue - which amounts to nearly 2.4 million cells (1024x768x 3 = 2,359,296). There's only a slim chance that all of these will be perfect; more likely, some will be stuck on (creating a "bright" defect) or dead (resulting in a "dark" defect). Read more

The RAMTester tool checks reliability of memory modules under MS Windows (x86 and x64), working with virtual addresses. It writes various bit patterns into memory cells and then reads them and compares with reference. Note that the check is qualitative, so you might want to use utilities working with real addresses under DOS to obtain more quantitative data. Read more