win32k.sys blue screen crash on Vista

Every time after I start the laptop computer, sometimes it crashes after 5 minutes (or longer) and restart.  It even crashes when it is waiting for me to enter the user login password,and then restart. 

There is a blue screen shows:
A problem has been detected and  windows has been shut down to prevent damage to your computer.
win32k.sys
page_fault_in_nonpaged_area

Technical information:
stop: 0x00000050 (0xFDC53002, 0X00000001, 0X970BC8FF, 0X00000000)
win32k.sys - address 970BC8FF base at 97080000, Datestamp 498f9e9d

The message is always the same.  I guess I have this problem since I tried to restore a backup file and it failed.  My computer runs on Windows Vista Home Premium service pack 1 (32bit).  1.73ghz Acer 5570z.  2GB Ram

PS.  The reason I tried to restore a backup file was that: when I use the browser (it happens on IE, firefox, or google chrome) to search the internet for a while, it just stop working.  it shows page not found.  However, I still can send and receive email. 

But now the blue screen is more scared than lost the internet connection on browser.  Does any one know any solution?

Thank you
Chris