I'm running Windows 8 Release Preview on an HP Pavillion Desktop PC. When I select the shut down option, I get an error message asking me to install a disk in the H: drive, citing a 'winlogon.exe' error with options to cancel, try again or continue. If I repeat click continue system eventual runs shutdown routine but won't shut down PC, only turn monitor off.

1. Have you made any changes on your computer prior to the issue?
2. Do you have any external memory devices connected to your computer?
Perform the following troubleshooting methods:
Method 1:
I would suggest you to perform System File Check (SFC), and then check if this fixes the issue.
Follow the steps:
a. Press “Windows Key + Q” to open Charms Bar.
b. Type “cmd” without quotes in the search box.
c. On the left pane, right click on the “cmd” option and select “Run as Administrator”.
d. Type ‘sfc /scannow’ without quotes and hit enter.

Note: It may ask for windows installation DVD to fix and to enable SFC to make more than minor repairs. Some files saved on your computer might get deleted when fixing corrupted files.

Method 2:
If that doesn’t work, then I would suggest you to refresh Windows 8 and then check if this fixes the issue.

Follow the steps:
a. Press “Windows Key + w”.
b. Type “Refresh” in the search box and hit “Enter”.
c. Select “Get started” option under “Refresh your PC without affecting your files” section.
d. Follow the on-screen instructions.

Important: Refreshing Windows 8 will remove all third party applications installed and it will reset all the Microsoft applications to default.