By running MemTest you can ensure that your computer's RAM is correctly functioning. It is wise to test this when you buy a new computer, install new RAM, or change the configuration of your machine (for instance, to overclock it). Are you the sort of user who likes to push the performance of your machine to the edge? Relying upon whether your machine will boot after your new BIOS tweaks is a poor way to determine the safety of your new settings. Use MemTest as a true test of stability.
To install just unzip into a folder of your choice. To uninstall MemTest, just delete the contents of that folder.