Sounds like a good machine. The 37GB hard drive is probably not the original as I think the 400MHz DV iMacs shipped with 10, 12 or 20GB drives.

It will make a very good OS 9 machine but Panther will also run acceptably well on it with 192MB RAM. If you can source a couple of 256MB sticks or even a 512MB stick then it would run Tiger at a very usable level.