New XPS 8910 tower won't wake up after sleep from keyboard or mouse

Version of Windows?

Reboot and IMMEDIATELY press F2 to open BIOS setup.

Look for an option "USB Wake" (or similar) and make sure it's ENabled. Be sure to save the change before exiting setup.

If that doesn't solve the problem (or USB Wake isn't listed in BIOS...

1. Open Device Manager and expand list under USB
2. Double-click a USB root hub and click its Power Management tab
3. Uncheck box "Allow PC to turn off..."
4. Repeat for all USB root hubs

Now expand list under Human Interface Devices in Device Manager

1. Uncheck that same box for any HID entry with a Power Management tab.

Then go to the Windows Power options page

1. Identify the current power plan and click link to change its settings
2. Click link on next screen for Advanced options
3. Disable USB Selective Suspend
4. Save the change to power plan if prompted

Reboot and see if problem is solved...