John,
Thanks a lot for the older script! (Although it was all for naught

)
By comparing the two I was able to modify the newer version (intended for Blender v248) so it works under Win7: I deleted all of the references to "os." Deleting them just removes some of the code which tries to keep you from writing to the wrong file name.
I'll attach a zip of my hacked version.
Unfortunately, however, Celestia can't handle meshes that are so big. It doesn't complain, it just silently doesn't load them at all, continuing on to load other models referenced later in the same SSC.
The ascii cmod for a 2K mesh is slightly over 2GB. The binary version created by cmodfix is slightly under 1GB. The binary cmod for the equivalent 1K mesh (which works fine) is about 60MB. Since Celestia is a 32bit application, I suspect there's some "sanity check" which skips the loading of very large meshes.
Code:
$ ls -l volcano_*
-rwxrwx---+ 1 selden None 974 Sep 20 13:20 volcano_1k10.cmod_material
-rwxrwx---+ 1 selden None 147880371 Sep 20 13:20 volcano_1k10.cmod_mesh
-rwxrwx---+ 1 selden None 59793998 Sep 20 13:23 volcano_1k10bin.cmod
-rwxrwx---+ 1 selden None 2130972320 Sep 21 08:45 volcano_2k.cmod
-rwxrwx---+ 1 selden None 905085264 Sep 21 08:53 volcano_2kbin.cmod
*sigh*
I guess I'll have to consider a workaround: either multiple meshes that are "small enough" or some other viewer entirely.
I'm sorry about your frustrations with Win7. Windows Explorer, the desktop file management GUI, is hard coded to protect files in the Program Files directories, regardless of their actual protections. The workaround that I use is to install programs in a different directory (C:\MyPrograms). Some people get around it by using a 3rd party file manager like Directory Opus. To avoid boot-time problems I either use a VM running under VirtualBox or plug in only the disk I want to boot from. It's more awkward than using a multi-boot loader like grub, but I don't have to worry about one O/S messing up the boot-time assumptions of another.