|Tell us the make and model of your brand name system, or if you have a generic desktop system, the make and model of the mboard. |
The specific model of a brand name system is shown on a label on the outside of the case somewhere, or it can often be determined by going to the brand name's web site and loading a program they have available.
For Dell computers, they have a Service Tag number - the specific model can be determined by using that on their site, or can often be determined there automatically by you downloading some software. The Service Tag number should be on a label on the outside of the case, probably on the bottom on a laptop, on the back on a desktop, and is often also shown in the bios Setup.
The model, sometimes the make, of a mboard in a generic desktop system is usually printed on the mboard's surface in obvious larger characters, often between the slots.
The model is often also displayed on a logo (graphical) screen early in the boot, but it's often not as specific as the specific model number.
Ram that works in another mboard , or any ram you buy or have lying around, may not work properly, or sometimes, not at all - even if it physically fits and is the right overall type (e.g. SDram, DDR, DDR2, etc.; PCxxxx, xxx mhz) for your mboard. In the worst cases of incompatibilty your mboard WILL NOT BOOT all the way with it installed, and the mboard may not even beep - the ram has to be compatible with the mboard's main chipset, or in the case of recent mboards, compatible with the memory controller built into the cpu.
See response 5 in this for some info about ram compatibility, and some places where you can find out what will work in your mboard for sure:
Correction to that:
Once you know which module ID strings (part numbers) work in your mboard, you can get them from anywhere you like that has ram with those ID strings.
If you have brand name ram, it is usually easy to look up whether it's ID string (part number) is in a list of compatible modules found by using your mboard or brand name system model number.
If the ram is generic, that may be difficult or impossible.
Mboards that use P4 cpus have been around for a long time.
Older mboards (e.g. made before 2002 or so) that use the original SDram are often limited to using 16 chip 256mb modules - 8 chips on both sides - they often recognize 8 chip 256mb SDram modules as having a 128mb capacity.
If that applies to your mboard model, new 16 chip 256mb SDram modules are hard to find these days, but you may be able to find used ones on the web.
"it shows inly 127 mb"
Some bioses subtract 1mb from the total amount of ram installed for the conventional memory amount that can't be used by the computer user, some don't. If the mboard has onboard video and you are using it (you have no video card in a mboard slot) , some bioses subtract whatever ram amount is being shared with the onboard video. Whatever total ram amount the bios reports is the same as what Windows reports in System Information as Physical Memory.