startup repair infinite loop

Hello,

My laptop specs:
Dell studio 1558 running Windows 7 Home premium (OEM preinstalled) 64-bit with SP1
Core i5 CPU with 4GB RAM
windows updates upto-date (enabled)
MS Sec Essentials upto-date - scanned 2 hrs before it was down.

Today my laptop suddenly switched OFF (by itself) and doesn't boot normally - Keeps going to startup repair infinite loop.

Tried:
startup repair - no luck
Booted with OEM win7 DVD and tried startup repair
Booted with OEM Win7 DVD and tried system restore
Booted with OEM Win7 DVD and tried registry hives recovery ( Startup Repair Infinite Loop Recovery )

but none of them worked.

Please advise.

Thanks
Prvn

Try pressing F8 as you boot your computer and select "Disable automatic restart upon System failure" on the assumption it may be blue screening then rebooting before you get the chance to read the error message.

Also, the fact the computer shutdown without any input from yourself suggests a corrupted update may be the culprit.

1) Scan th HD:
Disk Check

2)Check the hard drive with the manufacturer's diagnostic tools.
Hard Drive Diagnostics Tools and Utilities (Storage) - TACKtech Corp.
HD Diagnostic

thanks everyone who replied

seavixen32 - its not reboot, nor blue screen. It simply goes to starup repair every time i boot and tries to fix but no luck
Also, i couldnt get boot up menu by pressing F8 (tried many times but no luck)

seth500 - as i stated in my OP, i alredy tried that but no luck

theog - I will try this. The HDD is toshiba MK5056GSYF. can u suggest any tool to diagnose this?

txs
Prvn

Toshiba tools:
Software Utilities

Hi theog,

i ran chkdsk c: /f /r after booting thru DVD & at cmd prompt but no luck. (chkdsk showed it found few issues and fixed them successfully)

i tried running DOS ver of toshiba tool (by booting thru dvd and at cmd prompt) but it doesn't run and throws error "The subsystem needed to support the image type is not present" and tried to run windows version of tool but no use.

pls advise
Prvn

NOTE: i forgot to mention that i see "windows loading files.........." screen for 5-7 sec befor getting windows 7 logo and startup repair. I never saw this screen when my laptop was working fine.

Hi xarden, F8 never worked me to enter safe mode. I tried all poss of tap/hold f8 in the right time several times but no luck.

Well, finally I managed to fix it BUT it's not final!!

What i did:

1. ran chkdsk c:/c/f/r & sfc /scannow (no luck)
2. scanned with Kaspersky/bitdefender rescue disks (no luck)
3. booted with Win7 DVD and ran bootrec /fixmbr and bootrec /fixboot at cmd prompt (IT WORKED!!)

It ran for 3 days without a problem but again yesterday (19:50) it simply rebooted and going system repair continuously. I again fixed same way but got same problem again today (19:59). Again i had to fix it in that way.

Today, I did
- I did UNCHECK the "Automatically restart" in startup&recovery options.
- I also did both Rescue disk virus scan and virus removal tool run (no virus found by kaspersky)

Interestingly I got this problem only on those days I used HDMI port (to connect it to HDTV).

Please advise,
Thanks
Prvn