Ok, so I have an old Dell Dimension C300. It originally came with 128mb of RAM. I purchased 512mb x2, and made sure that it was "PC133U-333-542", and 133mhz - Just like the 128mb module that came with it. I installed the new RAM, and the computer turns on, but it says I only have 128mb of RAM still? Any help on this would be great

- Michael

See if there is a jumper on the motherboard to set the RAM amount than you check the system BIOS setup for any RAM setup. If all fail than you remove the 128MB RAM and plug in just the 512MB RAM only to see whether it is faulty. Than come back and let us know the result.

Right - I installed 512mb only. I accessed the bios, and it only shows 64mb

If the computer come with a manual, check it whether there is a jumper setting. Old computer use jumper setting rather than firmware. If all fail you may to take it to the vendor to verify the RAM is OK.

What is the max RAM capacity of the motherboard?

Come to think of it old computer have RAM limit. I don't whats the spec of your computer and I can't remember whats their limit. Correct me if I am wrong. For Pentium 3 it should be 512MB max but some later one has 1GB limit. For Pentium 4 the limit is from 1 GB to 2GB and the later one can go up to 4GB. But it also depend on the OS.

Motherboards have a RAM limit that they will support. Just because an OS will support the RAM does not mean the motherboard will. You will have to look up the model number online or look up the capacity in the user manual (or if it has jumpers they will tell you also)

Yeah, its a Pentium 4 and in the manual it says it has a maximum of 1GB

I only jumper I could find was the CMOS one

Mmm... in BIOS there MAY be an item labelled "OS install mode". Uncheck it. Never seen it, myself.
Just because you bought new RAM, it doesn't mean it is good. Always buy RAM with a lifetime warranty [which for a sys [or mb] is maybe 5, 8 years..:]. I have bought warranted RAM, it has failed... they just toss you a replacement over the counter. No questions.

Yeah, its a Pentium 4 and in the manual it says it has a maximum of 1GB

I only jumper I could find was the CMOS one

Than it should automatically detect your RAM. Than check the RAM slot to see whetyher it is clean and no dust in it. Use a brush and brush it gently. If all fail than the RAM could be faulty. Get back to your supplier and ask them to check for you and claim a new RAM.

I would recommend canned air over a brush....too much of a chance of static electricity on the MoBo.