Issue with an Inspiron M5040

Hello, sorry for my poor English (i am French but it is not an excuse),

My Inspiron M5040 (model 5040-0451) doesn't start windows since last week. When i restart the laptop i can see the dell logo and then the screen turn black and then i can see "__" at the top left of the screen and then... nothing. (no any more hard disk noise after 2 or 3 seconds).

I can run the diagnostic test. No problem detected. One point during this test, it is very long to complete the Hard drive test (about 10 minutes). After long test also no problem (System, Cables, OS Boot Path, Hard Drive 0, CD ROM, Viedo card, Notebook panel, primary battery, Charger, Processor fan, system management, Multi processor cache test, Memory Data bus Stess test and WCMch & WCMATS are passed). If i ask a test only for the hard drive the test result is strange because sometime it is written :

** Hard Drive 0 - DST Short Test **

Disk 0 is 20 percent complete.

Test passed

but 10 percent, 80 percent and 90 percent complete are not ont the screen (is it an issue ?)

If i try to restart the computer i get the same freeze screen than written above.

BUT one time (and only one) i did do the same process (boot > F12 > diagnostic > Reboot) and windows started normaly ! Of course i forgot to save personnel files on a usb key (shame on me).

Can you give me some help. In my opinion it is a problem with the hard disk or with the controller on the mother card.

Thanks in advance

Pierre

Other info coming for the diag process :

Hard drive O is OEM ATA product ST500LM012 HN-M500MBB rev 2AR20002 S/N: S2X1J90C523965, Type: SATA, seize 500GB

Buid 4210.3 ROM (i don't know what it is)

Nothing in Event log