Where can i download and install more ram on my latitude e5500 . it has 2 gig ram allreadybut i want extend to 4

Hello download the manual here:

http://support.asus.com/Download.aspx?SLanguage=en&m=P5L-VM%201394&p=1&s=22

The mainboard only supports up to 4 gb of ram.

To use the 4 gb, the ram type must be at equal size, inserted in the yellow or the black socket.

Good luck

Check www.crucial.com. Use the downloadable program to analyze your system or use the interactive menu system to explore your options.

Check online forums using google searches for terms like 'dell 5150 memory upgrade'. Sometimes, the maximum in the manual is not the real maximum. My Dimension 1000 laptop accepted a certain 1 GB card when the manual said the max was 256MB. Still running it after nearly ten years. The laptop was **** with 512MB (256 built-in and 256 add-on card) but the gf uses it every day.

If you are running a 32 bit version of windows it will only see up to 3.5gig of ram in your system no matter how much ram you put in there.
This is down to 32 bit windows only being able to address a maximum of 3.5 gig of ram.
Windows 64bit can address a far larger amount of ram and is why you will see all windows computers running 4gig or more of ram having Windows 64bit installed.
As you have said your computer is running Windows 7 32bit the only way you will get your computer to see the whole 4gig of ram you have installed is to upgrade to Windows 7 64bit.
Hope this answers your question and helps you out.

running triple channel memory with more than 3 DDR3 1600 sticks installed (4-6) cuts the memory speed in half. you have to run with 3 sticks at a time in triple channel mode or you will see a reduction in ram speeds.

OCZ is making some good 4 gig ram sticks. they have a 12 gig triple channel memory kit with 3x4gig sticks. you could get 2 of these kits and have your 6 sticks- 24 gigs total, but your memory frequencies will be lower- your ram access will be slower.

Have a look at the BIOS settings, the built-in video card may be grabbing 1Gb for video RAM. The video card uses shared RAM (part of the main RAM module/s). You can change the video RAM allocation in the BIOS.

There are a couple ways that help quite a bit. The internet is full of hints as well. As a tech Ill tell you the main things that most people miss.
First delete all files and uninstall all programs you do not need. Of course you will want to clear all your internet caches and delete the cookies you don't want.
When you are all done with the general cleaning run the disk defragmenter. Many people forget to do that and as their hard drives get fuller and fuller files get more and more fragmented.
Purchasing a newer much bigger hard drive will make access a little faster especially if it is a faster drive.
Purchasing more ram for the machine will likely help if it is marginal. For instance if you got one of those early Vista machines with 500 megs of ram. Bump that up to two gig and you should see a pretty big difference in Vista. If you have a 64 bit machine try bumping it up to 4 gigs. I like it about 4 gigs these days. 4 gigs of ram is standard for all new HP DV7 laptops.
Another thing that slows Computers is Anti Virus Programs. Do a search online for speed comparisons of the various antivirus programs. Mcaffee and Nortons are serious system hogs. I mostly use the free version of AVG or the paid version of Kaspersky. But even kaspersky is starting to get bloated. Some people dont like Antivir but I find it works reasonably well and is pretty fast.
Of course a virus can really cripple a computer for speed as can spamware.

Asus will explain why. Open the link provided and type, P5P800-VM in the Search window on the right upper corner; http://support.asus.com/download/download.aspx?SLanguage=en-us
Click on: P5P800-VM related FAQ.
Don't be fooled. I have installed XP 64bit and windows XP still reports 3GB.

Cheers!
Mike

Did you tried removing rams. Try putting a single ram and proceed with the installation and this way you will identify which ram is not functional...

Switch sticks around in various combinations (2 gig in slot one, 1 gig in slot two, switch, try other stick, etc) and see if it is the memory or the motherboard.

no need to install RAM in pairs.
you can buy and install memory but it should be the same model that you have now e.g. DDRII RAM Modules.
you can max out the RAM 4 gigs