Usually this is a sign of the power supply having taken some damage. If the system's still under warranty, call up Dell, have them send you a new one.
I have a dell inspiron 530 running windows vista. whenever i try to shut down the computer, it reboots. i turned off the "automatically restart on system failure" option in the advanced properties settings of my computer but that did not work. any suggestions on how to fix this? thanks.

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