Asus a7n266 c mbo has 1,512 ddr pc 3200 .an i add

DDR PC2700 or PC 3200 RAM is compatible.
Up to 1 GB per slot.
Here is a link to Crucial for RAM that is compatible:

Computer memory upgrades for ASUS P4PE Motherboard from Crucial com

amd processor? yes you can upgrade it and do not install the 256mb ram together with the 1 gb memory that you want to upgrade, better use the 1GB alone,

go by the law, youre only as fast as your slowest stick of ram, and PC2700 is about the most expensive ram out there.. old ram that is...
if i were you, sell those two, and buy yourself a stick of 512 pc3200..
i mean think about it mathwise...
if you go from 400 mhz ram
to 266 mhz ram
your going down in speed 33 percent...
sell em! =]

Yes. That motherboard can handle a total of 2048 (2 GB) of DDR PC 3200 (AKA DDR 400).

you can deselect from BIOS - CAS LATENCY TIMER to value 2, or better (2,5)

You do not say what memory you are trying to install.

The ASUS P4S800D motherboard has four memory slots that hold DDR PC2700 or DDR PC3200 with a maximum of 1GB per slot, so the installed maximum is 4GB.

DDR memory is generally available in 128MB, 256MB, 512MB and 1GB modules. If you already have memory installed, it must be at least 128MB so you cannot add modules to 'bring memory to 128'.

Either you have a different motherboard and posted in the wrong section, your memory calculations are wrong, or you have used older PC-133,PC-100 or PC-66 memory instead of DDR. The last is unlikely as older SDRAM has two notches and won't physically fit into a DDR slot that only has one notch.

Please re-post with the specific motherboard model just to confirm and a list of the memory modules you are trying to use.

hi

the highest capacity of ram is one gb

lucky

The ASUS P5RD1-VM takes the PC2700/3200 DDR SDRAM DIMMs. You can upgrade your ASUS P5RD1-VM to up to a maximum of 2.0 GB Memory, the system has 2 sockets to install Memory. For best system performance use the maximum amount of allowed Memory per slot for your system i.e. 1 GB.

Thanks
Iqbal

first u have to notice bus speed of old ram .it also 333[pc 3200]or not.

If you know how to get into BIOS; restore BIOS to factory defaults and try the DDR RAM again.