I made some progress. I took out the HDD and tried working on the SSD and that booted in AHCI mode with no problems, but needed to be initialised in Disk Management which required a full format. Not ideal but not the end of the world, and it now works fine. The HDD still wouldn't boot in AHCI so i booted back into Raid mode and noticed in Device Manager that there were 2 items flagged under Storage as Raid Controllers. I found the latest raid drivers on the AMD page and installed them and both the SSD and HDD appeared in this computer. However, the 2 partitions on the HDD had no sizes assigned, and if i tried to open one it crashed the system. I then booted back into AHCI mode and both drives were there, but again the HDD wasn't accessible. Even Disk Management won't open with them in the system, it just sits on "connecting to virtual disk service", plus windows doesn't feel right either - it takes much longer to boot up and installing software takes ages too. I tried to use EaseUS to look at the partitions but it won't open. I tried another version of it and that wouldn't open. I tried Paragon Partition and that wouldn't open either. I'm now making a bootable Gparted usb stick and i'll see if that can help, although i have a feeling the drive is corrupted or dead.