Bios setting

I have an old compaq deskpro xl 5133, i decided to format the hard drive and re install windows but i haveing trouble as it will not read the d: drive. all I need to know is hoe to enter the bios settings so i can switch the drive on. I have tried all keys from F1 to F12 but no luck please please please can someone tell me how to get into the bios settings on a compaq PC.
Thank You