There could be multiple issues.
I assume you have forgot the BIOS password. If that is the case then contact Sony support. They'll have few backdoor BIOS passwords that might help you.
If you're sure that you're entering the correct password, then try to reset the BIOS by removing the CMOS battery.
Follow the steps below :
1) Unplug AC adaptor.
2) Remove the battery.
3) Press and hold the power button for about 2 mins.
Possibly you could have your BIOS reset after this procedure. Some BIOS passwords don't reset even after removing the CMOS battery.
I assume you have exceeded the max number of tries to enter the BIOS by entering wrong passwords, it could have wiped out the OS and other files as a security measure.
simply, your HDD might have loose contact or corrupted.
NOTE : DO NOTHING if your machine is under warranty. Contact Sony