Corrupted drive, failed HDD, other things. All it tells you is it needs repair, but not what.
I usually boot off a Linux CD/DVD/USB to look around.
My computer randomly started runnin slow so I restarted it by power button . Then it refused to boot , only displaying this message :
Intel UNDI , PXE -2.0 (build 083)
Copyright <C> 1997-2000 Intel Corporation
For Atheros PCIE Ethernet Controller v184.108.40.206(09.06.12)
Check cable connection !
PXE-M0F : Exiting Intel PXE ROM.
Then it restarts and it shows again , restarts and again and again and again. What is happening ?