I have a Dell Dimension 4600 and tried 3 times before to install Windows 8 Pro 64bit. It always gave me the error for the execute bit not being set. So after much research, I went to Dell's Support site for the Dimension 4700C, and downloaded it BIOS update:
Now, I know what you are thinking. I been in the business of computer repair since 1987 and I have NEVER cross flashed a BIOS with another version because it would be most likely that it would not work, or it would brick the motherboard.
Well, I did it and then in the Security setting of the BIOS, sure enough, there was a place to set the execute bit. I did that and have installed WIndows 8 32 bit and 64 bit and Windows 7 all on it without any issues. Triple boot now......easy.......
MY DELL DIMENSION 4600 LIVES..........although now when it boots, it tells me it is a 4700C........what are the chances?