Windows

i would recommend downloading cpuz from the link bellow as it will tell you exactly what your motherboard is so you can find out what speed ram it can take and what the speed of your current ram is as you will need to match your new ram stick with it. E.g. if you have a pc100 stick that?s what you will need to get.

http://www.cpuid.com/cpuz.php

Hope this helps.

There are a number of limitations and issues when upgrading RAM on a PC.

First, if you are using Windows 95, 98 or Me, STOP at 384MB of RAM.
There is a bug in the core code that can trigger some slowdowns and even crashes if you exceed 511MB of RAM on a 9X PC.
The bug is VERY configuration dependant.

Next, SDRAM DIMM memory is NOT as generic as we would like.
I have seen far too many PCs that do not accept some DIMMs.
There are at least 4 structure variations of SDRAM DIMMs. Some motherboards accept almost any of the versions. Others are very finicky.

I recommend that you check for recommended RAM at one of the major manufactures:
www.crucial.com
www.kingston.com
www.pny.com

If you have a name brand system, or a name brand motherboard, they can let you know what the maximum RAM is, and what modules they recommend.

As to whether or not you can still use your existing memory, that will vary by the system and how it will deal with the new RAM.

For the most part, PC133 is downward compatible with PC100 and PC66 systems.
The density of the RAM chips on the module is actually more important than the speed.
Nearly all systems can use single density DIMMs.
Most will accept double density.
Only recent boards are apt to accept quad density DIMMs.

There is a good FAQ on memory at Kingston's site.

Chas

And TheChas is right on the money. [ans#2] Been there done that. We MUST have more info such as on MB video and OS???????

Depends on your Motherboard and what the bus speed is on it. If you are running a PII or PII under 900Mhz then the PC100 or PC133 should be ok. Newer systems may req that you get DDR and a few system from a 1 -2 yrs ago may even req rambus memory, consult your MB manual for the correct type and size of memory to install, or visit the MB manufacturer website to obtain the info.

Depending on how old your machine and the manufacturer will depend on the memory tpye. You can use pc133 in a machine that takes pc100 if you are not sure.

If your machine is a name brand, Dell, Gateway, HP, ect you can look up the specs on their website.

If it is a home built you can get the model of your motherboard and go to the manufacturers website and still get the info you need.

Depending on the os as others have said 98 has a problem above 512meg.

The memory that is currently in your machine might have numbers on it that could help.

Just be carefull while changing the memory. Touch the case before touching the memory. Static will destroy memory.

Good Luck Lee