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You asked this question on Microsoft but you asked it on the Windows XP forum. The suggestions were good for starters but were for XP. Here are the correct links for Windows 7.
Boot the computer using Last Known Good configuration:
Using Last Known Good Configuration
Perform Startup Repair and then check if this fixes the issue:
Fix Windows 7 using Startup Repair | 7 Tutorials
Startup Repair - Windows 7 Forums
After you get booted up, get back to us because it sounds like a hardware issue or a driver conflict. When you boot up, we can start investigating.