How do I tell which kind of RAM to buy?

Run Sisoft Sandra Lite. It will tell you everything you ever wanted to know about your system, and it is a free, limited version of their professional software.

It will generate a report and in that report there is an option to save the report. It saves as a text file. Look for info about your memory in that text file. Then buy the same kind at the store or online.

Or go to your manufacturers website and look up your model.

The simple way to check your memory is open your bios. In my experienced about computer the pentium 4 desktop the memory will use the DDR 266Mhz,333MhzD & DR 400Mhz. so before you will buy a memory of your computer you will need to check what kind of DDR memory you used now...

For example: if you were using the DDR 333 now inside your desktop so u will buy the DDR 333Mhz memory now.

Good Luck & God Bless

Sisoft Sandra Lite is nice and it will tell you what bays are used and what type they are.

It won't tell you what is the max the system CAN have or if it supports a faster type.

HP's website will tell you these things.

Crucial and Kingston's sites will tell you what chips they make that support your system.

And of course HP sells RAM as well.

system info,or like someone else said sisoft sandra.although you would be better of to take a chip out and write down all the info on it or take it with you when you go to purchase more along with other details of your computer.you cant always take what sisoft and simular programs say as gospel.

don't worry, any DDR RAM will do, if your system doesn't support the fastest rate let say 400MHz, it will run at 333MHz. This is the common answer.