It is most likely the monitor. It could also be the video card. What you need to do is:
1) Turn off the PC & the monitor. Unplug the cable from the monitor to the PC. Using canned air, clean the connectors on both items to remove any dust. Inspect the pins visually and make sure none are bent.
If this fixes the problem (it probably won't) you need to try a different monitor on your PC and your monitor on a different PC.
If it's the video card, your monitor will work on a different PC and the borrowed monitor will display the strange behavior your PC is experiencing.
If it's the monitor, the borrowed monitor will work on your PC and your monitor will not work correctly on the borrowed PC.
No two moments are alike and a person who thinks that any two moments are alike has never lived.