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before my computer went dead I sow an X on top of the battery

If an X appears on top of your battery: Symptoms The battery of a MacBook or MacBook Pro computer may: Appear to have no charge (zero percent) Be unable to power the computer by itself; the computer might work only when it is connected to the MagSafe power adapter, which only shows a green LED Appear with a black “X” icon on the menu bar Note: If a red “X” icon appears on the menu bar and the power adapter displays an amber LED, see MacBook, MacBook Pro, MacBook Air: Battery not recognized after being fully drained instead. Products Affected MacBook Pro, MacBook Resolution Shut down, then remove and reinstall the battery. Test for the issue(s) again. Connect the MagSafe power adapter (if you haven’t already) and see if the behavior continues. If the issue(s) persist, download and install the Mac OS X v10.4.9 Update. If the issue(s) persist, download and install Battery Update 1.3. http://support.apple.com/kb/TS1457?viewl

If you mean the symbol in the menu bar it states that the computer can’t detect a battery. Which Mac do you have?