HP has discovered a design flaw in some notebook memory modules that could cause frequent lockups and Windows' 'blue screens', the manufacturer is offering free memory replacements for those customers who have been affected.

HP believes that about 900,000 notebooks could be affected by the memory problem, said company spokesman Mike Hockey. To be affected, HP discovered, notebooks must combine the potentially defective memory modules with one of several Intel chipsets and Pentium processors that support a certain low-power state, dubbed C3, he said.