LVM upgrade on non-LVM system

I did a strange thing. I *wasn't* using LVM, but I think I accidentally installed it and device-mapper went all bonkers and decided to take all my drives away so I couldn't mount them:

fsck.ext3: Device or resource busy while trying to open /dev/sda1
in boot log. It appears that device-mapper usurps the /dev/sda# ... my old fstab won't work. But I'm not going to wipe it out!

What *finally* fixed it for me:
fdisk -l | grep "Disk" | grep -v "identifier"
This gives me a list of devices I *can* mount and what their sizes are. I ignored the "doesn't contain a valid partition table"
nano /etc/fstab
and changed my /dev/sda# to /dev/dm-# according to my carefully hand-written notes that compared the sda* to the dm-*. NB: the number after dm- does not necessarily map with the number after /dev/sda. My sda# skips 3 and 4. My dm-# does not skip, and also starts at 0.