This morning, my Precision T7500 had lights 2,3, and 4 blinking constantly with an amber power button.  Tried unplugging and letting it sit, but to no avail.  Finally I took out the 2nd CPU riser card, and the machine booted.  I tried looking up the light codes in the manual, but didn't find anything matching that pattern.  Does anyone happen to know, so I don't have to completely rip apart the machine to test the cpu and memory cards seperately?  It's a real pain to take off and get the main cpu heatsink reseated and screwed down...