Hello archer. Welcome to the forum.
If you are confident that the video drivers were installed clean and the video card works in another machine then the next most logical causes could be :
RAM - Run Memtest Memtest86+ - Advanced Memory Diagnostic Tool You can also test for a bad memory module by installing one stick in Slot 1 and testing, and then switch it out for the next stick, etc.
Power Supply - 450 watts is marginal for a high end video card. How many amps does it supply on the 12 volt rail? If it is an older supply it could be even more questionable. They get weaker as they get older.
Check your connections. Reseat video card and memory modules. Make sure the contacts are clean. Check all the electrical connections.
Overheating: Is the case and all the parts dust-free? If you take the side(s) off the case (and maybe blow a house fan into the case) and run the games does the issue improve?
Are you overclocking anything? This includes a factory overclock of the video card.
Try those and let us know what you find.