Nobody can help you without system information. Could be anything from insufficient user privileges to system restore to external disturbances like virus scanners.
Locate where user ID Photoshop Preferences are stored on your system. When you get Photoshop setup the way you like. Backup your User ID Photoshop Preferences. If you preferences then get reset in the future you can exit Photoshop and restore the setting you like from your backup.
Preferences are stored/saved when you quit the app. If Photoshop crashes on quit, your preferences will be lost. Crashes on quit are usually caused by font activation plug-ins.
The other possibility is a permissions problem. Try running Photoshop from a new Admin user account.
What system infomration you need??
it is Windows 8 Genuine 64bit...(Dell Optiplex 3010).Using default windows defender.
Tell me if more infomration is required
Did you try running under a new Admin user to see if the preferences were retained between sessions?