HP has warned that a flaw in some laptop memory modules causes them to fail when used with Intel's power-management technology.

The flaw affects a number of memory modules made by Samsung, Infineon and Winbond and has put the kibosh on HP's plans to let customers swap out memory, the company said. Modules made by Micron are subject to a different flaw related to memory clock synchronisation.

A Samsung spokeswoman said the company was investigating the issue and representatives for Infineon, Micron and Winbond have yet to respond.

Intel's processors use power-management techniques such as throttling back the clock speed or shutting down portions of the chip when those areas or transistors are not required by a particular instruction stream. When it does this, it puts the memory module into what is called self-refresh mode, explained Ronald Kasik, director of customer engineering and sustaining marketing for HP. The memory chip can move into, or out of, this state thousands of times a second, he said.

The problem occurs under certain conditions when the memory module tries to leave the self-refresh mode and reactivate. This can cause the memory module to fail and crash the system, resulting in data loss. Micron's memory modules can fail under certain conditions when the internal memory clock and external memory clock fail to synchronise as the memory is read at a high rate of speed, Kasik said.

Users will only experience these types of system crashes under very rare conditions, Kasik said. However, HP is recommending that users of the affected notebooks download a utility from HP's website that will identify whether they have one of the flawed memory modules, he said.

The affected notebooks are Compaq Evo Notebook N610c, N610v, N620c, N800c; N800v, N800w, N1000c and N1000v; Compaq Presario 1500, 2800, x1000 and x1200; HP Compaq Business Notebook nx7000, and HP Pavilion zt3000.

Users who detect the flawed memory modules can sign up to receive a new memory module in 128MB, 256MB and 512MB sizes, Kasik said. The user will be given a screwdriver and instructions on how to replace the module themselves and can return the flawed module to receive a free 32MB USB Thumb Drive from Trek 2000 International.

HP believes the problem extends to any notebook manufacturer that is using memory modules from the above companies and Intel's mobile technology in their notebooks.