I am wanting to double the exisiting 512MB PC3200 DDR 400Mhz memory module to my son's PC. The existing 512MB module that is fitted is manufactured by Elixir and is labelled 512MB DDR 400Mhz CL3 PC3200U-30330. To play safe I've tried to source an identical memory module but this particular brand seems to have sold out. Would I be able to purchase any other brand of DDR PC3200 memory? If so, what do I need to look out for and could anyone recommend a company to purchase the item from?