I've had another read of your first post. This is how I now think you intend your rig to work:
1. The boot drive is always on IDE and this is BIOS enabled & prioritised for booting.
2. The other 3 drives are fitted with the SATA adapter, presumably all drives set to Master (not sure it matters but that's what I woud do).
3. A SATA cable for each IDE disk is taken to the mobo, presumably connected in low to high port number order (again not sure it matters, but that's what I'd do).
4. SATA is enabled in your BIOS.
Now, if I read you correctly, connecting the data disks to SATA allows you to hboot fully but without having the SATA connected drives recognised.
Is the above correct?
Yes.
IDE is prioirity and only boot-from selcted. I disabled everything else.
All drives are jumpered to Master.
All extra drives are connected to MoBo starting with SATA1, respectively.
SATA is enabled on in BIOS, but RAID is not.If so, DimaYasni makes a good point in his last post.
In your position, I'd do exactly as you have done - seek help from a forum before dumping the idea of using a SATA converter.
What would my next step be? I'd buy a single SATA 2 HDD and fit that, expecting it to work. If not, then you'd need to run your mobo diagnostics (or you might have done that already) to check everything out at system level.
If that works, then you can get your data off the IDE drives by slaving them in turn on the IDE channel and copying across to the SATA drives you will have purchased.
Does that make sense?
It does. I know it would be wise to replace the IDEs with SATA for multiple reasons but I was hoping not to have to give them up. Being the MoBo only has the one IDE socket, it limits what I can connect. I have one internal and one external CD/DVD, so I could remove the internal leaving two IDEs slots available for two IDE drives.
I think as a last resort, I may move all data from all drives to my 1TB external, format them (including my boot drive), connect all as SATA (with no IDE) and do a fresh install of XP and hope for the best...