Just to test: can you try removing the added RAM again just to see if the system works differently?

all right. I will try .
today,the restart error happened again over 10 times.
I want to rescue&recover the system if it is not because the memory. you know that the IBM thinkpad X40 has no CD-ROM, so the rescue&recover is in the hardware, but I forget the password
of the rescue&recover, can you help me to enter the rescue&recover ? do IBM have the administrator password of rescue&recover?

Here are a couple of links to IBM/Lenovo Rescue & Recovery page:

http://www.pc.ibm.com/us/thinkpad/xs...let/index.html

http://www-307.ibm.com/pc/support/si...cid=MIGR-56102