Satellite C855D-S5340 help plz

[MutesToCry]

So I bought this Toshiba satellite C855D-S5340 from the pawn shop (already CPU clear semed brand new) it worked perfectly well until a few days ago when I tried to factory reset it but my little sister saw it was deleting everything and purposely turned it off while it ddid it (was at 30%) and I tried restoring it but it didn't work then it kept saying no bootable device I look up for days trying to fix it I bought a new screwdriver then un screwed it and fix it and put it back together but when I booted it up this time it asked me for hdd/sdd password and I never remembered it for I pressed enter went black except for the "_" and then I waited 1-2 min nothing idk what happened do I need to replace my hard drive if I do how much will it cost and where can I get it for cheap Plz help me I have import work to do

 

[AsadP2012]

Replacing the hard drive is a quick and the easiest option in your case.
Here are some options (They have to be 2.5")

WD 750GB - £37.32
http/www.ebuyer.com/497319-wd-750gb-blue-internal-2-5in-hard-drive-wd7500bpvx

Seagate 500GB (16MB Cache) - £32.86
http/www.ebuyer.com/448875-seagate-500gb-momentus-thin-hard-drive-st500lt012

Seagate 500GB (8MB Cache) - £32.99
http/www.ebuyer.com/284651-seagate-500gb-momentus-spinpoint-m8-hard-drive-st500lm012

I'd personally stick to the WD 16MB Cache one if you want a faster working hard drive.