Version names

Quite so but unfortunately if I want to produce a script
that has no dependencies then I need to use what is provided
in Windows and Windows batch commands seem to be the best
way to do that.

Batch scripts are also quite dependent on the system and settings used. 
Moreover what are you trying to do? The rwXXX scheme is just a 
suggestion, every user is free to change the name during the 
installation, so there is no way to know by folder name which version 
you're dealing with... The only half-way sensible solution I can think 
of is looking for Rterm.exe and running each one to get the 
corresponding R version - I suppose you can do that with a batch script 
;).

If all you want to do is to determine the current (most recently 
installed) R version, then all it takes is two lines of C code [just 
read one registry entry] - and it's at least as portable across Windows 
systems as a batch script, but far more flexible. (There may even be a 
way to get that info w/o coding at all - I'm not sure whether regedit 
has any batch mode or something ...).

Cheers,
Simon