Windows XP: Environment Variables Bug

I just encountered a strange bug in the way that Windows XP handles environment variables.

Setting the variables in the GUI-Editor, it can be reproduced like this:

alpha = %busy1%\ddd
busy1 = %busy2%\test
busy2 = c:\
zulu = %busy1%\ddd

Save the settings, open the commandline and do some tests:

C:\>echo %alpha%
%busy1%\ddd

C:\>echo %busy2%
c:\

C:\>echo %busy1%
c:\\test

C:\>echo %zulu%
c:\\test\ddd

This means, that windows can resolve %busy2% in %busy1% but NOT %busy1% in %alpha%. Interestingly it CAN resolve %busy1% in %zulu%.

This only gives me one possible interpretation: Some recursion in the environment variables system of windows XP seems to use alphabetical sorting.

Any hints where this might derive from?