HD failing need to move os to new bigger HD

This question may have been posted and answered at an earlier date but I am experiencing some complications that I am unsure how to address. My desktops Hd recently started failing and so today I ordered a new one that is 250gb larger. I understand how to back up most of my files and have an external to do so but I do not have install disk for the windows 7 os as my computer came with it installed. My product key for my os is still on the sticker on the side of the tower but as this new Hd is 100% blank i need to move the os somehow and I am unsure as to how I am supposed to do this. I have read alot about cloning a Hd but am wondering if this is my best option. ANY information on this problem would be greatly appreciated but please keep in mind i am no computer genius, Thank you all for any and all help.

   Information

We always assume you have made your Recovery Disks using the OEM manufacturer's Recovery Media Creator app the first day you had your new PC.
& made the Startup Repair CD.
startup repair disc-create

Did you make the OEM manufacturer's Recovery Disks?

Have a look at those tutorials:
Best to backup to a external HDD.
System Image Recovery
Backup Complete Computer - Create an Image Backup
Restore Backup User and System Files


SSD - Install and Transfer the Operating System

i have never created a backup or recovery disk but the old hard drive is still accessible atm. My problem is I do not have windows seven installation disk so if I follow the steps in the Backup Complete Computer tut you linked me to i do not know how to make the created backup run on my new and empty hard drive. Unless the backup is already bootable?

Take a look at Step 9.
Backup Complete Computer - Create an Image Backup

Thats what I was just reading into lol, My concern was that it says a repair disk cannot install windows seven only repair it. Once I create the back up and save it to my external do I just install the blank hd pop in the repair disk and point the clone or, backup rather, to the empty drive?

right but the repair disk itself wont have the os on it will it? Sorry im so confused lol. I thought I was creating 1. A back up of my c drive and then 2. A repair disk.
After I boot the repair disk I thought I would need to locate the back up files and move them to the new hd by clicking system image recovery

1) Make a image of your HD Drive.
Backup Complete Computer - Create an Image Backup
2) Make a startup repair disk.
System Repair Disc - Create
3) Recovery the image to new HD Drive.
System Image Recovery

yes thats what I thought lol and image can be saved to an external correct

Yes, Best to backup to a external HDD.