RE: Dell DESKTOP XPS will not detect monitor or hard drives?
2 years old is not a new computer. Do you see anything when booting? How do you know it is powering up? You cannot test the hard drive by adding a diff one. If you see anything on the screen when first booting, reboot the computer and immediately start tapping F12 to get to the diagnostics on the boot menu. Try using a recovery or repair disk if you cannot get to the boot menu. Test everything. If you don't get any errors, reboot and run the diagnostics again, but this time select Custom Test of hard drive to check the whole drive. Probably a failed hard drive or failed video card.
Always post your actual model name but do not include any service tag or other personal info--for instance--XPS 8700