Check for infection by installing Malwarebytes
in Safe Mode with Networking, updating and running a full scan. If it won't run, download, burn to CD or write to flash stick and run a full scan with Microsoft Standalone System Sweeper
If it finds infection boot into DVD/Repair CD to run Startup Repair again repeatedly.
Did you actually run Startup Repair
three separate times with reboots in between, or just boot into Repair console? What did it report after each?
Open the disk's Command line to run bootrec /fixmbr
and bootrec /fixboot,
close command box and reboot.
Then if Windows 7 doesn't start boot back into disk Command Line to run SFC -SCANNOW Run in Command Prompt at Boot
, followed by Disk Check.
Then test your HD using maker's HD Diagnostic
extended diagnostics/repair CD scan. Next test your RAM - Test with Memtest86+
Sometimes booting into free Partition Wizard
bootable CD, confirming that Windows 7 or it's 100mb System Reserved partition (preferred) is still marked Active, then clicking on HD to highlight it and running from Disk tab Rebuild MBR will work to start Windows 7 on its own. If this fails, change the Active flag to Windows 7 partition itself if it's not now there. Then try Rebuild again, followed by 3 Startup Repairs.
If all this fails you've tried everything and can now follow the steps I gave earlier to copy out your files and run Factory Recovery or clean reinstall. Now's the chance to get a superior clean reinstall with a Windows 7 Installation DVD following the steps I gave you - just let us know which verison and bit rate your license is for if you don't have the DVD.