Hopefully, you have kept a backup of your data somewhere ...else.
Windows 7 Directions:
1. Boot from the Windows 7 DVD.
2. Select
Repair my computer.
3. Select
Command Prompt
4. From the command prompt enter the following command:
Chkdsk /R C: where "C" is your boot drive.
5. Answer
Y to check the disk the next time that the system restarts.
6. Reboot the system. After the reboot, Windows will check the hard disk and try to repair the damaged area.
7. If you still get the error after this process, repeat the process but try rebuilding the master boot record at the command prompt with the following command:
bootrec /fixboot and then rebooting
If your system can be saved, you should now be able to boot back into Windows without a problem.
Obviously, you cannot boot any recovery partition Dell may have provided because your drive won't mount. You are going to have to try using tools you access from a USB port or
CD drive. Which means at some point you have to change the boot sequence to boot from these other devices rather than the hard drive. On power up, you press F2 until the Bios comes up and make the change to boot order there.
You can download and burn the hard drives manufacturer's diagnostics to a CD and boot them from there. Or burn the Ultimate Boot CD. It has many manufacturer's diagnostics upon it.
Frequently Asked Questions
https://www.dell.com/support/article/us/en/19/sln128947/my-dell-computer-did-not-come-with-disks?lang=en