Factory restore Latitude E5420

I got this Dell Latitude E5420 with Win-7 Home on C-Drive. I installed the Win7 Ultimate on C-Drive as well. Everything worked fine , earlier windows folder is named to Windows.old. I can still see the
Recovery ---> D:\Dell|image\Factory.wim file (It's almost 6GB)

How can I factory restore my Latitude E5420? I tried F10/F11/F12 CTL-F10, CTL-F11,CTL-F12 etc. at boot and nothing happened.

Thanks

 

According to the Dell Guide for this, they say you should use the Windows Recovery Environment if you need to factory default and didn't make a system backup:
Using the Dell Backup and Recovery Manager - KB Article - 370333 | Dell

Otherwise, if you paid for the recovery disks, you can boot from them and use that directly instead.

 

Those are the old school Dell recovery partitions.

You need to fit F8 for Advanced Boot options and select Repair My Computer. Let it load and hit next for system recovery options, type in your Windows password. The next screen is actually system recovery options, the bottom one should be Dell DataSafe Local Backup/Restore/Recovery something to that nature and that is how you activate the recovery partition on a Vista/7 Dell computer.