If you don't have disks then how were you able to format your HD already? Or are you using the word "format" to describe some other repair attempt you've made?

You need a Repair CD to attempt repairs if you haven't somehow overwritten Win7. System Repair Disc - Create

Boot the Repair CD and run Startup Repair repeatedly: Startup Repair Report back to let us know what happens.

If Repairs don't work, try marking Win7 partition active to see if they work then: Partition - Mark as Active

If no luck, then you need to find a way to Recover or Reinstall. If Win7 came pre-installed on your computer, you should have either made Repair Disks when you set up your computer or you can run the Recovery Partition by tapping the key given for Factory Recovery on the first screen. If you don't see it, look in the Manual on the Support Downloads webpage for your computer model. We can help you find it if you tell us your computer make/model.

If you have no factory Recovery then you need to find any Win7 installer to clean reinstall using these steps: re-install windows 7

You can copy out your files first using the Repair CD or Installation DVD: Copy & Paste - in Windows Recovery Console