If none of the above resolve your problem:
1. Use the Registry Editor to export HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\RasMan\PPP\EAP to a SaveEAP.reg file, in case you need to restore this key.
2. Delete all of the sub-keys except 4 and 13.
3. Use the Services applet in Administrative Tools to configure the following services Startup type as Automatic:
- Remote Access Auto Connection Manager
- Remote Access Connection Manager
4. Shutdown and restart Windows XP.