FixYa is a product support website, and as such we do not delve into manufacturing. No we cannot supply ram memory.
I can supply you with the solution to your questions, however.
This is HP Support, and the main page for the Pavilion 513n Desktop PC,
http://h10025.www1.hp.com/ewfrf/wc/product?product=90384&lc=en&cc=us&dlc=en&submit.y=5&submit.x=6&lang=en&cc=usIf you click on > Product information > Product specifications > HP Pavilion 513n Desktop PC Product Specifications,
you can view,
A) What type of ram memory the computer uses,
B) How much is the Maximum Total Amount for the computer,
C) How much is the Maximum Amount for EACH ram slot,
D) How many ram slots
Look under the Memory heading.
A) What type of ram memory
Type - DDR
It's DDR Sdram
Speed - PC1600/PC2100
Tells you either PC1600 can be used, or PC2100.
PC1600 is DDR Sdram that operates at 200MHz.
PC2100 is DDR Sdram that operates at 266MHz.
{To expound:
Ram memory operates at a Frequency Rate. Slang for frequency rate is 'Speed'.
Mega = approximately 1 Million
Hertz stands for Cycles per Second
Example: PC2100 is DDR Sdram that operates at 266 Million Cycles per Second }
B) What is the Maximum Total Amount for the computer. (Motherboard)
According to HP it is 1GB.
{Maximum - 1GB (2 X 512) HP recommended maximum}
I believe this to be wrong. The Total Maximum Amount is 2GB.
1GB per ram slot.
I base this upon using the memory configurator's of several websites, that sell ram memory for the Pavilion 513n desktop computer, and looking at what the motherboard chipset for the Pavilion 513n will support.
The motherboard chipset is the Intel 845GL.
This chart found on Wikipedia, states what the Intel 845GL chipset will support,
http://en.wikipedia.org/wiki/List_of_Intel_chipsets#Pentium_4_ChipsetsAs you can see reading across from the 845GL subheading, and looking under > Max.memory, 2GB is listed.
Sources for online memory configurators,
1) Crucial.com
2) Tigerdirect.com
3) Newegg.com
4) Memory4less.net
In this case,
C) Maximum Amount for EACH ram slot is 1GB.
D) There are Two ram slots. {Proper speak for ram Slot is ram Bank}
Kingston is a good brand for economical ram memory.
So is Ultra.
An easy way to find out what type of ram memory you need, and how much is the Maximum Total Amount, as well as the Maximum Amount for Each ram slot, is to use an automatic scanner from a website that sells ram memory.
The above four websites listed, are but a small handful of the total websites online that offer an automatic scan.
Let's use Crucial.com for an example.
On the main page,
http://www.crucial.com/,you will see - Scan My System, in blue.
Simply click on it to run an automatic scan of your computers hardware.
Doesn't look at your personal effects, just the hardware of your computer.
After the scan is done, you will be presented with the ram memory info you need.
Several options of ram memory are presented for you to choose from.