in the device manager do your ide controllers and the likes have !'s next to them or are they unknown devices with ? marks.
You first should try updating the chipset drivers (this usually updates the ide drivers too)
If this doesn't fix it then it could be a virus. Ive seen boot sector viruses such as the monkey and anticmos virus cause problems with the drive (and cdrom) recognition in windows 9x series. Those viruses can only infect fat partition types so if you have an ntfs partition its safe.
other than that there is the possibility of the noide setting in the ios.vxd section in the registry (disables ide cept already mounted volumes such as the hard drives) but if it his is a fresh installation i highly doubt it