My Thinkpad R61 turns itself on when I plug it in the AC

[Djmax4599]

Sometimes when I plug in my Thinkpad it turns itself on I hear the fan and then the laptop cuts off and it shows the indicator lights like normal when your about to turn on your Thinkpad.. Then I push the power button to turn it on it turns on normal and I see the Thinkpad logo. A few seconds later I see a message that says bad Cmos and I hear beeps and it takes me to the bios. So I set the time and the date because it changed itself to 1/1/1998. If your wondering I am using it with only the AC plugged in.. Please help

[ganon11000]

Sometimes when I plug in my Thinkpad it turns itself on I hear the fan and then the laptop cuts off and it shows the indicator lights like normal when your about to turn on your Thinkpad.. Then I push the power button to turn it on it turns on normal and I see the Thinkpad logo. A few seconds later I see a message that says bad Cmos and I hear beeps and it takes me to the bios. So I set the time and the date because it changed itself to 1/1/1998. If your wondering I am using it with only the AC plugged in.. Please help

Its basic, but have you checked the CMOS battery? (Little button cell battery normally wrapped in plastic with 2 wires coming out)

[RealBlackStuff]

Yup, you must replace the CMOS battery.
This will work: http://www.ebay.com/itm/NEW-IBM-THINKPA ... 0249381604