Q:
Recently my Acer Aspire 7520g laptop got some problems: I started system as usual, and nothing happened, then I left for a while, and when I returned to the laptop, it already turned off. When I tried to start it again, system began repeating starting continually as disk rotated. Power auto started and then stopped automatically again, it just repeated the operation over and over again. And the only method to stop the loop is to remove the battery. As the process happens within 4 seconds, so I have no way to enter BIOS so far that system keeps restarting continually. I even removed the old disk and change a new one, but the problem seems still unsolved. I also checked up memory slot, no any problem. So should I change the motherboard? I just bought it one year ago, its system is XP Pro version. Anybody got the similar problem ever before? Hope to get your help, thank you so much!
A:
1): Once I repaired a similar problem for one of my customers, and I suggest you following my next steps:
 Start up and press F8 and keyed –s (means to enter with single user mode) and press Enter.
/sbin/fsck “press blank” –fv, and press Enter
/sbin/mount “press blank”–uw “press blank“/ and press Enter

Ouch “press blank”/var/db/.AppleSetupDone  and press Enter
Password “press blank” root and press Enter (after pressing Enter, system would ask you to set up password, when type password, cursor would not display *, when finish entering password, press Enter, and at this mom