Install memory in Dell Latitude C640

Go here and see your options:

http://www.crucial.com/store/listparts.aspx?model=Latitude%20C640%20Series&Cat=RAM

This site is your best choice for support, price and quality.

How to reset The Latitude C640 Bios password?!

1.First flip your laptop over and remove the battery, as well as any cables connected to the laptop.
2.Remove the screw latched into the memory panel on the bottom of the computer found near the rear.
3.Lift the panel off and expose the memory modules.
4.Seek for a small push-button and press it, holding it for about two seconds. Reassemble your laptop and start it up.

Thank You!

It appears to be the issue with the ram. Turn off laptop, remove battery and unscrew the the cover to the RAM. Its on the back panel. Remove and reseat the RAM after cleaning the gold pins.

You can also use the Microsoft memory diagnostic tool.

i dont think the c640 usually comes with wireless so i dont think the antenna will be in there so you might have to get them. but you can take off the ram cover on the bottom and see if the wires are there. this shows the wireless card in there
http://support.dell.com/support/edocs/systems/latc640/sm_en/upgrades.htm#999869

Here are the max memory and speeds:
Lat C640 is Max 512M per stick DDR-266 (PC2100) or DDR333 ( PC2700 ) for a total of 1024 Meg

Lat D520 is either 2 or 4 Meg total. DDR2-667 ( PC2-5300 )
Although the memory can be installed one module at a time, the best performance comes from using matched pairs of modules.Maximum memory for systems with the Intel 945GM chipset is 4096MB, maximum memory with the Intel 940GML chipset is 2048MB
Lat D430 has only slot with a Max of 1 Meg. You can use DDR2-667 (PC2-5300)  or DDR2-533 (PC2-4200)

Lat D420 is a max of  1.5G    . Use 1GB DDR2-533 (PC2-4200)

Inspiron 2200 is one slot with a max of 1280 Meg. recomended is 1GB DDR-333 (PC2700)

Here is a link to find almost any memory you need:
http://www.crucial.com/index.aspx

NOTE:
When mixed speeds in the same PC, the memory will run at the slowest speed installed or the highest speed allowed by your system, whichever is slower.

Good Luck

plz try by resiting the ram

You cannot change the memory settings in BIOS. All you need to do is go into the bios screen. confim that it has seen your new memory and "save and exit" If it is not showing your new memory try removing and reinstalling the memory confirming it is installed correctly. it should just see it.

it's underneath the computer, behind a small panel held down by 1 or two screws..open that panel up, and either add the memory or remove what's in there, and replace it..make sure you are wiped clean from ESD(electrostatic discharge) before you touch them.

available physical memmory is what all your programs on your comp is using like windows virus software drivers im thinking you probably have spyware or bugs in your comp that could be bringing memmory down

total physical memmory is what you just put in

Sounds like either there is not enough memory in the laptop to handle what you want it to do, or the operating system needs to be restored. I would try the latter of the two, because that is cheaper, and then if that does not work, then upgrade the RAM