These artifacts are random and can be created in multiple ways, although they occur rarely. The cause appears to be a failure by some part of Windows' code to erase a segment of the screen. The only way that I know how to make an artifact disappear is to restart Windows.
For example: After right-clicking on a file folder in Windows 7, I see hovering over the desktop an artifact that is a highlighted blue bar with the word Open in white letters.
From my own experience, this can occur with Windows XP, 7, 8, and 8.1.
Are there other ways to fix this besides restarting? Thank you.
update: while not a solution for everyone, and imho not a real solution for my question, this worked today (no future guarantees) ... an artifact today was really annoying me to the point of wanting to reboot ... when i plugged my second monitor into the laptop's HDMI port, the artifact vanished, possibly because this caused a refresh of video memory cache. 2015-06-10
next time if this random happens, i'm going to try changing the screen resolution temporarily and then changng it back. could work?! end update