Upgrading RAM

[sadio8]

Quick question here.

I want to upgrade the ram in my sister's desktop computer.

Right now the memory on the computer is as follows:

512MB DDR2 SDRAM at 533mhz

So, when i am looking for ram i see the following:

http://www.canadacomputers.com/index.php?do=ShowProdList&cmd=pl&id=RAM.346

There are many categories of DDR2 RAM:

DDR2 1066 PC2-8500+
DDR2 1200 PC2-9600
DDR2 400 PC2-3200
DDR2 533 PC2-4200
DDR2 667 PC2-5300
DDR2 800 PC2-6400+

Which category can I pick where to get RAM from? Does it have to be from the "DDR2 533 PC2-4200" category?

Likewise from here:

http://www.tigerdirect.ca/applications/Category/category_tlc.asp?CatId=10&name=Memory-RAM

The following are DDR2 RAM subcategories:

PC4200
PC5400
PC6400
PC8000

The following are also DDR2 RAM Dual Channel subcategories:

PC4200
PC5400
PC6400
PC8000
PC8500


Can I only select ram from the PC4200 category? I was just basing this off the fact that from this link, http://www.canadacomputers.com/index.php?do=ShowProdList&cmd=pl&id=RAM.346 , the "DDR2 533 PC2-4200" had the same 'speed' as the current RAM installed on my sisters desktop (512MB DDR2 SDRAM at 533mhz).

So if anyone can help me out that would be great, i don't even know if i'm going about this the right way!!!

Thanks!!:D

[Vietnamese Crippler]

You can go with higher clocked RAM, but your motherboard has to be able to support it. Since I don't know your computer/motherboard/etc. specs, I'd just go with the same specs as what you have right now.