> Did you change the SATA controller mode to RAID in your system BIOS when you tried to use Intel® Rapid Storage Technology? If the answer is no, your system should not have a RAID volume created.
No, I did not set a RAID myself (never even thought of setting one up!) - I was flabbergasted when it appeared on my machine after the IRST installation.
>It seems that the operating system became corrupted. You may want to restore your system to a previous date before Intel® Rapid Storage Technology was installed.
Of course I tried that, to no avail: going back enough in time, the restore uninstalled not only IRST's GUI, but also applications that were installed before IRST... but the disk nevertheless stayed "Controlled by RAID" 8-O. And when I subsequently tried to switch to IDE in the machine Setup (POST, as suggested by the "removdrv.txt" document), the result was BSOD during Windows startup - only switching back to RAID in POST made Windows start again properly (as I explained in my original post).
I do not think the OS is "corrupted", because everything else works just fine (and every disk check turns out ok). But anyway, I have now successfully moved the contents of my HDD to a 512GB SSD (including the bootable OS), and have the two disks working fine in the machine. They are both still controlled by the RAID (given that I can't get rid of it), but it doesn't seem to be doing any harm, so switching to IDE became a moot issue - I'll simply keep the RAID, hoping it will be ok in the future.
But still: not being able to undo IRST's fiddling with my machine without a total reinstall of everything looks extremely inelegant to me.
Thank you for your help!