Recognising 4 IDE Hard Drives

Have a Win98SE machine using 4 hard drives on both the IDE channels.
i.e. Primary Master & Slave & Secondary Master & Slave.

I am unable to get Windows to recognise the 4th drive once I remove a CD Rom Drive (used to setup) & then attempt to add the 4th drive.

I get errors on both the drive & also secondary IDE channel in Device Manager.

Using a ASUS TULS2-C Motherboard

A fellow tech suggested it may not be possible due to limitations with Win98.

I must unfortunately use Win98.

Need to know if he is right or if another solution (apart from Promise Card) exists to be able to use existing setup.

Thanks in Advance