Acer Aspire one. XP operating system. Machine has not been connected to the Web. When I start the machine and it askes for the password, but on entering the assigned password some times the machine rejects the password. When it accepts the password it will operate ok. Some times i will not shut down. Pressing the power button for long period dos not close it down. Have had to take the battery out to close the computer down. Has any one any ideas please.