occasionally when I approach my PC the screen is black but the computer is running but when I try to access it, the screen stays black. The monitor and the computer is on so I assume it is locked up and try to power it off on the tower but it will not power off. I end up having to turn it off and back on at the power strip and then the system will come up and work properly. What do you think is going on?

Do you have standby or hibernate enabled? If you do, disable them & reconfigure your power scheme settings.

Go one step farther. Turn it off completely when not in use. Check apm or acpi settings if available. Be sure to press the space key to try to get monitor to come back on. Might take a minute or so to wake. See event viewer logs. "Best Practices", Event viewer, host file, perfmon, antivirus, anti-spyware, Live CD's, backups, are in my top 10

The hibernate was enabled. I disabled then reconfigured my power scheme and it seems to be working fine. Thanks for the help