RE: XPS 8900 freezing
If you haven't updated all of the drivers listed on the Dell page for updates on your XPS 8900, recommend that you do this first. Use your service tag number to go to the correct system info for your XPS 8900.system.
Next recommend that you access the Intel Rapid Storage Technology Icon (mine is located as hidden icon in the system tray at the bottom right corner of the monitor screen) and locate the Performance section. Disable Power saving feature and then reboot the computer. Doing this helped stop freeze occurrences and gave a very noticeable increase in performance and speed in accessing programs for me.