How to Reinstall Windows 7 on a locked bootloader?

[Gerard_7]

I and my college mates received brand new HP Pavilion g4 notebooks as part of an initiative by a local political party group to garner support from our age demographic.
These laptops however came pre-installed with Windows 7 professional and a linux distro called BOSS on GNU GRUB.
I have included pictures of all the screens involved in the process.
Here is the boot sequence:
Power button> Political party Logo > GNU GRUB bootloader asking me to choose either Windows 7 or Linux> Windows
I've tried hitting the esc key on boot up. Pics included.

http://imgur.com/a/zFbYT
Its been 2 years since and the performance has become very sluggish and I would like to reinstall windows. However, the exact process to achieve this in this particular situation eludes me.
This laptop doesn't have a DVD drive, just USB ports.
How can i install a fresh windows 7 and also get rid of the linux os as Ive never used it?
Thanks in advance!

 

[bicycle_repair_man]

You can get rid of the Linux distro by deleting the partition it's installed on.

As for reinstalling Windows, most off-the-shelf PCs have a hidden recovery partition that reinstalls the OS. Normally, it's accessible by pressing a function key during start-up.

 

[Gerard_7]

Thanks for your response bicycle_repair_man. My priority is to reinstall windows first. Ill try to find this recovery partition and will update this thread of my efforts.

Update:
Ive tried tapping the F11 key on boot, it gives a series of warning beeps and then proceeds to GNU GRUB loader, ignoring the key presses. The other function key brings up the BIOS menu.

 

[Kitanul]

If you have access to another computer, you can make a bootable usb to install Windows 7, just find a windows 7 iso and use something like https://rufus.akeo.ie/
Plug the usb, boot on it, format everything, and install

 

[Gerard_7]

Thankyou for your input, Kitanul. I can download and make a bootable iso of Windows 7 Professional 64 bit( the OS it presently runs on), but how must I proceed upon serial key validation?

 

[bicycle_repair_man]

If you have the license key (usually on the underside of the laptop or in the battery compartment) then you can use that to re-activate Windows. Just make sure that the edition is exactly the same as what's currently installed.