For future reference it's known as a USB flash drive. USB stands for Universal Serial Bus- it's a kind of connection port used on newer computers. But 'stick' works too.
So let's try and make this a little more simple. I'll give you step-by-step directions. What we're going to do it put some information on a USB flash drive, then tell the computer to go to the flash drive first, instead of the hard drive. The info on the flash drive will fix the hard drive, and the 'NTLDR is missing' problem will be fixed.
On a working computer, click here to download the files you will need.
Right-click on the download folder and select 'extract all'.