I'm browsing the collection of images that I use to index our attic. (Hierarchical data structures are most easily represented using the native folder system.)
I open one in the OS X image viewer app. I rename it in the folder while it's open. The application handles it, changing the name on the fly.
Windows doesn't do that.
PS. The OS X 10.4.x TextEdit application is such a reasonable lightweight substitute for Word, that after some reflection the best way to get a decent RTF file format word processor on the G3 iBook is to buy Tiger for the iBook! (My research suggests it runs quite well on a G3 with 640MB DRAM and I get the educational price.)