access to track pad panel in System preference is impossible

Restart your computer and try again.

Launch the Console application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad. Click Utilities, then Console in the icon grid.

Step 1

Make sure the title of the Console window is All Messages. If it isn't, select All Messages from the SYSTEM LOG QUERIES menu on the left. If you don't see that menu, select

View ▹ Show Log List

from the menu bar.

Enter the name of the crashed application or process (System Preferences) in the Filter text field. Select the messages from the time of the last crash, if any. Copy them to the Clipboard (command-C). Paste into a reply to this message (command-V).

When posting a log extract, be selective. In most cases, a few dozen lines are more than enough.

Please do not indiscriminately dump thousands of lines from the log into this discussion.

Important: Some private information, such as your name, may appear in the log. Anonymize before posting.

Step 2

Still in the Console window, look under User Diagnostic Reports for crash reports related to the process. The report name starts with the name of the crashed process, and ends with ".crash". Select the most recent report and post the entire contents — again, the text, not a screenshot. In the interest of privacy, I suggest that, before posting, you edit out the “Anonymous UUID,” a long string of letters, numbers, and dashes in the header of the report, if it’s present (it may not be.) Please don’t post shutdownStall, spin, or hang logs — they're very long and not helpful.

Back up all data.

Boot into Recovery by holding down the key combination command-R at the startup chime. Release the keys when you see a gray screen with a spinning dial.

Note: You need an always-on Ethernet or Wi-Fi connection to the Internet to use Recovery. It won’t work with USB or PPPoE modems, or with proxy servers, or with networks that require a certificate for authentication.

When the OS X Utilities screen appears, follow the prompts to reinstall the OS. You don't need to erase the boot volume, and you won't need your backup unless something goes wrong. If your Mac was upgraded from an older version of OS X, you’ll need the Apple ID and password you used to upgrade, so make a note of those before you begin.

If you're sure you know when the problem started, you can restore your whole boot volume from the last snapshot made before then. You'll lose all later changes to your data.