My Lenovo ideapad u165 freezes

I have an 11.6" HD Lenovo Ideapad U165 with AMD Athlon Neo K325 1.2 GHz, 2 GB DDR3 RAM and ATI HD4200 Graphics. The laptop randomly freezes and there's nothing I can do. I have to remove the battery then boot it up again. Is this a memory issue or BIOS?
