coolmangs123...
Do you by chance have a graphics card installed in the PCIe slot? I have had this same thing happen on a similar SFF PC when a graphics card went bad. Exact same symptoms...
Other possibilities are failing power supply, failing hard drive, bad RAM. All of these require testing to determine. To do this you would need some sort of boot disk with tools for performing the tests, assuming you can even boot to a cd/dvd. You could remove the drive and attach it as a slave in another PC and run tests either from a boot disk (more reliable) or from Windows...
