the folder of WINDOWS\assembly of WinXP cann't be copyed in Vista

There are two OSes installed in my computer, one is XP, the other one is
Vista .
1. Under Vista:
I Logon the Vista OS by administrator accounts , When I copy the
folder (the XP's windows dir ) "d:\WINDOWS\assembly" to anywhere, an error
happened .
“the file 2.0.0.0__b03f5f7f11d50a3a can't be found in the path of
d:\windows\assembly\GAC_32\System.EnterpriseServices�
And, when I use the API function Findfirstfile() , with the parameter
"d:\windows\assembly\GAC_32\System.EnterpriseServices\2.0.0.0__b03f5f7f11d50a3a\*",
an error happened too. GetLasterror code is 3 (The system can not find the
path specified).
And when I use the command line with "cacls
d:\windows\assembly\GAC_32\System.EnterpriseServices\2.0.0.0__b03f5f7f11d50a3a\*
/G everyone:F " failed too. The message is “ the path can't be found � too.

2. under XP:
But when I logon the XP by the administrator accounts ,the folder (XP's
windows dir) “WINDOWS\assembly� can be copied to anywhere. for example, copy
to "e:\test".

3. Vista again
I Logon the Vista by the administrator accounts again, the folder
"e:\test\assembly" which is copied in the step 2 can be copied to anywhere
successfully.

question
1.Why the folder "d:\windows\assembly " can't be copied under the Vista OS,
2.but can be copied under XP OS?
3.Why the folder’s copy can be copied successfully under Vista OS ?

Please help me , I need your help. Thank you!