[C#] Ou se trouvent ces constantes ?

Microsoft Windows XP [version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.

C:\Documents and Settings\HP>SET
ALLUSERSPROFILE=C:\Documents and Settings\All Users
APPDATA=C:\Documents and Settings\HP\Application Data
CLIENTNAME=Console
CommonProgramFiles=C:\Program Files\Fichiers communs
COMPUTERNAME=HP
ComSpec=C:\WINDOWS\system32\cmd.exe
FP_NO_HOST_CHECK=NO
HOMEDRIVE=C:
HOMEPATH=\Documents and Settings\HP
LOGONSERVER=\\HP
NUMBER_OF_PROCESSORS=1
OS=Windows_NT
Path=C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem
PATHEXT=.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH
PROCESSOR_ARCHITECTURE=x86
PROCESSOR_IDENTIFIER=x86 Family 15 Model 1 Stepping 2, GenuineIntel
PROCESSOR_LEVEL=15
PROCESSOR_REVISION=0102
ProgramFiles=C:\Program Files
PROMPT=$P$G
SESSIONNAME=Console
SystemDrive=C:
SystemRoot=C:\WINDOWS
TEMP=C:\DOCUME~1\HP\LOCALS~1\Temp
TMP=C:\DOCUME~1\HP\LOCALS~1\Temp
USERDOMAIN=HP
USERNAME=HP
USERPROFILE=C:\Documents and Settings\HP
windir=C:\WINDOWS

C:\Documents and Settings\HP>exit