No OS stated, XP? VISTA,
'ok its HP but old but not too old, 2008\
in the magic year of 2006 HP added the F11 key to the old Compaq line. (hp bought)
so if the PC is still 100% HP and the hard drive not slammed with alien MS disks, from MS. then the recover partition works
so power on F11 hammer f11 fast, and bingo F11 recovery runs. pick fix startup files repair
fails still then reload the whole OS now back to DAY1.
all HP do this 2006 to now.
all do unless is bad or was bad long ago HDD bad, HDD SLAMMED.
my guess you ran DBAN, and why not fess up and say the full name of the product, (app) or there web site you got it URL
then we know what you did,.
DBAN erases it all the HDD is just empty space
and F11 is gone gone for ever more.
then you can do this.
see the 6 ways here, #1 is now erased leaving 5
#2 is gone at HP this old.
#3 is your best bet.