Hd only Boots through windows boot manager

guys I need help with a problem , my grandpa's pc stopped working so I reinstalled windows on it I did it on my on pc and it worked fine but on his pc it didn't work then I putted it back on my pc and looked at the boot options an saw that if I told the pc to boot in the hd I'd wouldn't work unless it was on wbm but my grandpa's pc is older and doesn't have wbm do you know how I can solve this issue?
(Sorry if I wrote something wrong English is a foreign language for me )

I forgot to mentions my specs
Msi gaming 7
Core i7 4790k
8 gig ddr3 kingston 1866 MHz
Gtx 970 gigabyte windforce

Grandpas
Asus p5kpl - 1600
Random 4 gig 2x2 kit
Core 2 quad
GeForce 9500gt

The hd in question is a brand new wd blue

Don't know the exact problem but generally installing Windows on one computer then putting the HDD in a substantially different computer does cause problems, even when putting the HDD back in the computer used for the installation. Best solution is to re-install Windows on your grandpa's computer if it will boot to the DVD. Another thing to try is to create the System Repair disc on your computer then boot to it on the other. Both computers have to be either 32-bit or 64-bit.

Thanks but the problem is that he's computer doesn't boot from a usb and I have no cd/DVDs around

Berton said:

Don't know the exact problem but generally installing Windows on one computer then putting the HDD in a substantially different computer does cause problems, even when putting the HDD back in the computer used for the installation. Best solution is to re-install Windows on your grandpa's computer if it will boot to the DVD. Another thing to try is to create the System Repair disc on your computer then boot to it on the other. Both computers have to be either 32-bit or 64-bit.

You also have no idea what could be the problem because I checked out and my own pc only boots from its sad if I choose wbm if I try to go directly to the sad it says that there is no bootable devices ask me to put one and re start

Did you enter BIOS setup on Grampa's computer to see if Legacy USB is enabled? Try that now.

If so then you should be able to boot a flash stick if it is correctly formatted using Windows 7 USB-DVD Download Tool
with an ISO that is known good and for the exact version that came with the PC.

You can read more about obtaining and formatting the installation media in Step 1 of Clean Reinstall Windows 7
which also compiles everything that works best to get and keep a perfect install.

whs said:

I am afraid you will have to invest the 50 cents and get a DVD, Then install it on your grandpa's PC. I am sure grandpa will refund the 50 cents.

The problem is not the dad price but I don't have a car and here in Brazil it's actually hard to find somewhere they sell this kind of thing and the price us about 2,50 U.S. Dollars (taxes here are a bit above 100%)

It looks like the problem is that the windows installed uefi and the old pc apparently doesn't support uefi so...
Got it working out so tanks for every one

Windows can't install UEFI without a UEFI BIOS.

How did you end up installing it?

We'd better see a screenshot of Disk Management - Post a Screen Capture Image since half the time we ask something is incorrectly configured.