Asus G73JH boot problem

[abstract]

Hi i am having a serious problem with my lap top. My problem started about a year into owning my laptop. The problem is that when i turn it on it takes much longer at the asus loading screen to then just finally go to a black screen displaying only a blinking _ (underscore). depending on my boot option it will then display a message telling me to reboot and select a proper boot device. these are the following things i have tryed

-Switching around boot orders to try and have it boot from CD/DVD, usb drive, or HDD
-pressing esc to select boot device that way
-taking out HDD in different orders or having non in with just a boot-able dvd in the disk drive
- i have tried changing multiple boot settings in my bios and all sorts of settings just to see if it may change anything
-I have pulled my cmos battery once for about 10 sec
-i have tried a repair dvd and a full windows 7 install dvd


Nothing seems to be doing the trick i have gottin into a blue window threw a usb boot device but there is only a default selection that gets me no where it counts down from 10 but when it hits 0 it just starts all over again. So im just wondering if anyone has any other ideas on what i could try next. Or if someone can tell me its the mother board for sure and i can just replace it. any hints tips or advice would be greatly appreciated. thanks in advanced.

In addition 1 of my laptops fans broke and it had a terrible over heating problem even when i mounted a 120mm fan to a box to blow air into the laptop it would still get hot. it has over heated and shut down many times because of its poor cooling untill the 120 mm fan that is. could this have messed up the mobo ? is it possible for a mobo to still display bios and recognize boot options but not be able to access any of them due to hardware failure ? thanks again

 

[smorizio]

first off pull the hard drive and if you can by an adaptor or a usb to laptop cable and see if the hard drive is see in another system.(Also you may want to try and pull any data off that hard drive.). with the drive connected if you can see it and get your data try a hard drive fitness test. with the laptop off and the battery out flip it over and reseat the ram on the unit. over time ram can walk out. if after you reset the ram go into the cmos and hit factory defult then hit save and exit. connect a bootable usb or cd in the drive and see if you can boot from it. (memtest iso). windows if it can find a hard drive will reboot or stop.