Hi all I was doing a memory upgrade and I was wondering, the computer has 256mgs of pc133 in it and I wanted to put one stick of 512 pc 133 and when I do it only reads the 512 no more. its only one or the other any ideas, could it be the bios? its a dell dementions 4100.

try swapping the 2 memory chips around and see if that makes any difference, I had a same problem this morning and fixed it by doing just that. Windows XP Home Pentium 4 3.0ghz 256mb DDR 120gb Hard Drive ATI Radeon 9200 Series 16x DVD Dual Layer RW Mart

It's a density issue...basically, you have the wrong type of RAM. Almost all PC133 RAM produced these days is high density & your board apparently needs low density RAM. If that 512MB stick only has 8 chips, it's almost certainly high density RAM. Another possibilty is your board only supports a total of 512MB. If you only have two slots, that's a distinct possibility. Check your manual of the Dell website. This will explain the density issue: http://support.gateway.com/s/tutorials/Tu_851378.shtml Asus A7N8X-X 1800+ @ 8 x 210MHz 768MB PC3200 Asus A9550 128MB/128-bit Gamer Edition WinME/WinXP Pro

Did you check your Dimension 4100 memory matrix requirement ? You have a total of two slot for a max 512MB configuration, also your system most likely requires the older low-density (double-sided) ram. If you compare the initial 256MB and 512MB that you just got are they physically identical. If the 512MB is single-sided (high-density), you will need to replace it with a low density stick. However with your Dimension 4100 supporting max 512MB, I'd suggest you just keep things they way they are now. Do not type anything in this space.