Trouble with BIOS?

I have on my pc two hard drives. Recently, I reinstalled windows xp on drive c. When both drives are physically connected BIOS shows in BOOT section only the second drive, name it the small one, and windows doesn't start. I become on black screen the message "Reboot and Select proper Boot device or Insert Boot Media in selected Boot device and press a key". If I disconnect the small drive and restart the BIOS in Boot section is shown drive c having on Windows which works properly. If then, with working windows, I reconnect the small driver windows doesn't see it. Even in Disk Management it isn't scown up. Being thankfull of your tip on what to do.