You want to boot the 64 bit Repair CD which Bill linked to, after burning it at 4x speed with ImgBurn (never fails).
See if it finds an installation and then offers a Repair and accept it. If this does not start Windows 7, then boot back in and click through to Recovery Tools list to run Startup Repair repeatedly - if it finds an installation then it is normally reparable.
System Restore is automated along with all other repair commands in Startup Repair, but you might try it separately if necessary. Can you remember what it was you were doing that might have caused the problem?
From what Johnny is saying, that model has a built-in Recovery partition which can be triggered as given. You should try that as a last resort. If Recovery will not run using his approach, then read the Manual on the Support Downloads webpage for your model. There is an image file in the Recovery partition which can be mounted and run to reinstall, as well.
If you need to retrieve files before reimaging or reinstalling, use Paragon Rescue free app. First try to rescue partition, then files which can be copied off externally. You can also reinstall with any installer for your version, and any version installer can have all other versions unlocked using ei.cfg removal tool.