Are the drives capable of cable select? Try setting them all to cable select and seeing if they're detected.
Also, are they SATA or PATA drives? If they are PATA, and the hard drive is on the same IDE cable as the CDROM drive, try changing the drive to another cable. Having them on the same one doesn't normally, but can cause trouble.

Also, does the BIOS detect them? If it does, you could have a problem with the filesystem on the drives. For example, XP won't recognise a drive with the ext2/3 Linux filesystem, or Win 98 won't recognise a drive formatted in NTFS.