Recently had Avast installed and the resident protection will not start up after firdt use when password was established. Using Windows XP on high speed internet.
What password? the avast one or the Windows, logon password?
Do you have any other antivirus in your system?
Can you try to repair your installation?
Go to Control Panel > Add/Remove programs > avast! antivirus > Remove. Then choose Repair function in the popup window (Repair). You must be connected to the internet while repairing.
If this does not help, can you uninstall / boot / install / boot again?