If you can't boot into the DVD then do you have the Repair My Computer choice on F8 Advanced Boot Options?
If so boot into it to run Startup Repair
repeatedly, post back results. Run Memory Diagnostics from F8 menu if available.
If not reset your BIOS to defaults: Clear CMOS - 3 Ways to Clear the CMOS - Reset BIOS
. Then see if you can boot DVD by setting it first to boot in BIOS setup, or tapping the F10 key for Boot Menu. Are you prompted to "Press any key to boot DVD?" and what happens if so?
Once you can boot the DVD choose Repair on second screen then run Startup Repair to see what it reports.
Next burn to CD and run 5-6 passes of memtest86: RAM - Test with Memtest86+
Next burn to CD or write to flash stick, boot and run a full scan with Microsoft Standalone System Sweeper.
Once the System is clean if it won't start boot into System Recovery Options
via the F8 menu or disk as shown in tutorial, run Startup Repair
repeatedly no matter what it reports. Post back results.
If this fails, try System Restore from Recovery Options list, then if that fails open a Command Line to run SFC -SCANNOW Run in Command Prompt at Boot
Next test your HD with maker's HD Diagnostic
extended CD test.
As a last resort boot free Partition Wizard
bootable CD to Explore C to see if your files are intact, make sure C or the 100mb System Reserved partition (preferred) is marked Active
, then click on HD to highlight it, from Disk tab select Rebuild MBR, Apply. If Windows 7 doesn't start and you restored Active flag, run Startup Repair 3 Separate Times
If these all fail you can copy out your data using your Windows 7 DVD or Repair CD: Copy & Paste - in Windows Recovery Console
or Paragon Rescue CD. System Repair Disc - Create
Then run Factory Recovery from its partition or disks you made or order from Tech Support, or find a Windows 7 installation DVD to clean reinstall using Product Key on COA sticker: Clean Reinstalling Windows 7