LCD monitors should be set to 60hz. I don't believe this issue has anything to do with the monitor though....
If what your describing is that, when dragging one window over another, little "pictures" of the top window appear in the bottom window, then this is caused by the bottom window not repainting.
So the question to ask is "why isn't it repainting"?
Does this happen with all programs? If so, it would appear that your PC is simply underpowered, or having it's power gobbled up by something else on the system- one candidate, for example, is malware.
For the curious- the cause is rather down-level. Every window has a function that windows calls- it basically tells it, "hey, the user clicked on you" or "hey, you need to repaint". what causes the "ghosted" images is that when windows moves one window over another and exposes part of a window beneath it, it sends that windows function a message saying "hey, you need to repaint this area". if the program is busy, however, the message is not received right away- instead, it's added to a queue- sort of a "to-do" list for the window. This can happen if the program is doing some intensive task- reading files, saving a big document, etc. However- as you said, this is not normal behaviour and should really only occur under specific circumstances.
If it's happening with <all> your windows, and this is a recent occurrence, I'm inclined to believe you may be a victim of an infection.
To determine wether this is the case you can visit the malware section of this site:
follow the guides posted
here and then make a new thread/post in the spyware removal section
here; you'll need to post the logs from hijackthis, Super Anti-spyware, and Malware bytes Anti-malware.
