Computer Won't Boot

Hello,

I am having issues with my Dell Inspiron N7010 booting up (Windows 7). I have had it for a year with no problems and then after a system update that either Windows or my security system (McAfee) performed, it will not boot. F8 on the start-up screen will not work and the one time I tried to get into Safe Mode it stalled halfway through and would not open. It automatically goes to 'startup repair' but after attempting repairs always says it can't perform any, and I have tried system restore from four different points and they all come up with error messages.

The same thing happened about a month ago after updates were installed but that time F8 was working, and eventually I got a screen that asked if I wanted to try logging in anyway which worked perfectly and I had no other problems until this month's run of updates. However, I cannot recall how I got that option in the first place and am currently at a loss after having tried everything on the Dell and Windows websites to fix this.

Any help would be greatly appreciated.