Some things you can try...
1. Verify that the indexing service is turned off.
2. Check the settings in PowerDVD, see if it's checked for hardware acceleration. It may run better not using hardware acceleration.
3. Just for troubleshooting, try disabling any wireless cards you might have.
4. Run msconfig (start-run-msconfig). Under the startup tab disable all, reboot and try your player. If it solves the problem, re-enable each startup item and test individualy to find the conflicting program/driver.
5. If all else fails, try a different program to run DVD's