420 boot up issue Intermintent

From time to time I boot up my 420 and it just goes to a fast blinking cusror directly after the bios load. It pause there and does nothing else. The first time it happened I was able to try to reboot a couple times and eventually it came up but first went to the screen that asks which mode I want to boot up to.

This last time it tried rebooting over 20 times without luck. I decided to go into the Dell test utility and performed a quick test. It did find an error (F00:137B).  I tested some things indepenedly as well like memory and the hard drive but nothing failed.

I have a feeling its a failing HD but I can find no evidence.

Please advise.

Thanks.