Question Insperion 620

[wlkin]

I decided to upgrade my Dell Insperion 620 after my bricking my Alienware 17 r2 by updating the BIOS. I replaced the powersuppy in the 620 with a 650w. Computer worked just fine. About a month later, I replace the old cpu with a new one making sure the pins lined up right, added some grease reinstalled the CPU fan. Plug everything in and hit the start button. PSU and CPU fan twirled for about 5 seconds and stopped. CAT 5 connecting was blinking like it was trying to receive info from router, red light on motherboard. Went back to old cpu and have the same problem. Hooked up the old PSU and have the same problem. No video, POST, so I cannot tell what is going on. Any suggestions as to what might be wrong will be most welcome.
Bill

 

[wlkin]

More info. Went thru the posted checklist. Most of it don't apply. Just changed the CPU with the new PSU that was working. Will go thru the post similar to mine to see if any of those will help.