How about replacing them with a single SATA drive?
SATA hard drives are cheaper than IDE anyway.
I regret not upgrading my old PC to SATA. When I needed to replace the hard drive, I made the mistake of buying an expensive slow IDE drive, rather than getting a SATA controller and SATA drive which would've be about the same price. Of course, I didn't realise this at the time - you live and learn.
It should be fairly easy to copy all data from the two IDE drives to the new SATA drive using a free program such as Clonezilla. Clonezilla
I doubt you'll be very happy with four drives on a single IDE cable because only one drive can actually be read or written to at a time your system will probably perform worse than it did when you had two IDE ports.
I guess your suggestion will work well in my special case.
After windows start I received a message about erasing unused desktop icons. Of course I clicked "No", but windows made a thorough cleanup of all drives, thereby moving windows from drive C to drive H and deleted what it found to be useless, amongst the deleted files also MS-Office and all saved files within the folder.
So I'll kick off the two IDE-HDDs and replace them with SATA.
The "restore" feature didn't find any changes done within the last month.
The desktop clean up wizard is a pain and needs to be disabled. Right click anywhere on the desktop, click properties, to get display properties, select the desktop tab, click on customise desktop and uncheck the run desktop cleanup every 60 days box. See my attachment.
I've found the restore function to be of limited use and tend to disable that too because it saps the performance.