Modify the following value within HKEY_CURRENT_USER:
Software\Microsoft\Windows NT\CurrentVersion\Winlogon\ParseAutoexec
1 = autoexec.bat is parsed
0 = autoexec.bat is not parsed
FYI:
http://support.microsoft.com/kb/124551/en-us/
Modify the following value within HKEY_CURRENT_USER:
Software\Microsoft\Windows NT\CurrentVersion\Winlogon\ParseAutoexec
1 = autoexec.bat is parsed
0 = autoexec.bat is not parsed