Why does Lenovo laptop automatically shut down after it starts up with two transient sounds

I bought the Lenovo ThinkPad r61 series notebook in. Because the company can take my computer to work, I often carry my computer to work and get off work. One day I took my computer to work as usual. As a result, when I got started, the title was displayed. At first, googlebaidu said that the BIOS may be faulty and I suspected the memory, the hard disk was not saved. I finally installed the disassembled machine. Suddenly, I thought about it. It is very likely that the battery's bayonet was not locked. It took a long time, when I pulled it out of the bag, I screwed the battery interface to the open state. It is estimated that Lenovo's computer had this test. It would take the bayonet to lock the screen to make the boot normal, in short, this is a strange problem.

In addition, I found that the machine could not be turned on again today, and a fan error appeared on the black screen. So I only learned that the fan may have been used for a long time, but it seems useless to remove the fan from the dust, it seems that you want to change the fan. when the power is turned on, you can try another fan after a while. However, you can press ESC to enter the system when the power is turned on.