Hewlett-Packard has discovered a memory flaw in as many as 900,000 of its notebook computers and is offering customers free memory modules as a remedy.

HP said Friday that through tests, it discovered a circuit design flaw in some notebook memory modules that could cause Windows operating system "blue screens," intermittent lockups or memory corruption.

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.

The memory modules in question, which came in 128MB, 256MB and 512MB capacities, were manufactured between March 2002 and July 2003 by four companies, including Infineon, Micron, Samsung and Winbond, Hockey said.

"HP has been in contact with us on this issue, and we are in the process of finding a suitable solution," said an Infineon representative. None of the other companies was immediately available to comment.

HP believes the memory flaw could cause problems in other PC makers' notebooks as well, because some of them could have used the same combination of parts.

HP is asking customers who own specific notebook models to download and run a software utility to test their machine for the flawed memory. The utility can be found on HP's Web site. The company will replace the modules that are found to be defective at no charge to the notebook owner, by using the Web site to collect their information.

HP will mail new modules to customers with affected machines. The customers can install the modules using guidelines posted on HP's Web site, the company said, and they will be required to return the defective modules via a prepaid envelope included with the replacement component.

"We're doing what's right for the customer," Hockey said.

HP notebook models affected by the replacement program include Compaq Evo Notebook models N610c, N610v, N620c, N800c, N800v, N800w, N1000c and N1000v as well as Compaq Presario models 1500, 2800, x1000 and x1200, the HP and Compaq Business Notebook nx7000, and the HP Pavilion zt3000.

Those notebooks use the combination of the memory modules, a Pentium 4 or Pentium M processor and one of several chipsets, including the Intel 845MP, 845MZ, 852PM, 852GME or 855PM with discrete graphics, Hockey said.

HP's replacement program will run through the end of this year.