Why does my Dell Vostro have a Toshiba hard drive?

On April 25 2015 I contacted Dell Warranty about my hard drive acting up on my Vostro 3750. They ran diagnostics, concluded it was faulty (HardDrive-Targeted Read Test;CFI:N;KYHD:N;DD:N;DR:N). On April 27th they shipped a replacement under the service request number 910355792. So when it arrived I exchanged the drives and returned the faulty one. Now fast forward to December when I was able to install Windows 10 Pro. Microsoft's website only had a few requirements to run it, mainly RAM, graphics processing, and a up-to-date OS to start with. I was unaware that Dell had a whole list of computers that weren't to be tested with W10. The install went along fine and I let it update all the necessary drivers, having preinstalled only enough for it to start and connect to the internet to update. I was unaware that one of the device drivers didn't get installed and my computer seemed to be running just fine. Then about two weeks ago it started getting slow. I noticed it would start to freeze up a little but it would always unfreeze quickly. Then one week ago I was writing a paper at night(College Sophomore so this computer is pretty much my life) and closed the lid for the night. Now the battery life is already pretty bad so needless to say it died over night, but when I went to turn it back on it took it forever to come on. Easily 10-15 minutes just to make it to the log-in screen. I got it unlocked and brought it back to my office to plug it back in on my desk where it stays almost religiously. I then got on Dell Support, which is where I finally found out the 3750 wasn't tested with W10, and ran a quick diagnostic which said the hard drive, which was listed as a TOSHIBA is in critical condition and needs immediate replacement. At this point I had to see what was going on, so I opened Device Manager went to disk drives and lo and behold it says my hard drive is a TOSHIBA MQ01ACF050. Well that's weird. So I checked my event viewer to make sure and it was indeed migrated, configured and started when I cleared it and installed W10 back in December. There was also an unknown device in the event log which is how I found out about the missing driver. Then to top it off the administrative event log had 16,000 events from the minute I installed W10 till today almost all of which just say harddisk0\DR0 has a bad block. duh. So I am in the process of saving all our important documents to a external hard drive and I guess I will revert it back to W8 but what I really want to know is why did Dell Warranty send me a Toshiba hard drive. Any advice on any of these issues would be sincerely appreciated.