I tried to install Bitdefender Free on a Windows XP computer that had AVG. I removed AVG but Bitdefender failed to install. (Gave a "failed" message.) I tried to reboot the computer but only get a black screen after seeing Bios messages and the hard drive light stays off after Bios messages. So, I thought maybe the hard drive had just failed on this VERY old computer. I was also trying to install Bitdefender on a second computer. Well, the second (also an old Dell running XP) did THE SAME THING! I cannot see anything after the Bios screen. Did I just fry two hard drives????!!!!
After the Bios screen, "Loading PBR for descriptor 2...done." flashes on the top left corner. I had to record it with my phone so I could pause it to read it. Then the screen goes black and the hard drive light is off.
I guess my brain was asleep last week. This morning, I used F8 to get to Windows boot options. I was able to "Restore to last know good configuration". So, if anyone else has a similar problem, don't forget about F8!