Buy Desktop Memory How To Know Which RAM Memory To Buy? (Desktop Computer)?

How to know which RAM memory to buy? (Desktop computer)? - buy desktop memory

Ok, my computer has 512 MB of RAM, but I want to update it. I do not know what to buy though. My RAM is written to DDR http://crucial.com 3.33/PC2700 and the results of the analysis were: the maximum storage capacity: 1024 MB
Currently Installed Memory: 512 MB
Memory Slots Available: 1
Number of Banks: 2
Dual Channel Support: NA
CPU Manufacturer: GenuineIntel
CPU Family: Intel (R) Pentium (R) 4 CPU 3.00GHz Model 2, Level 9
CPU Speed: 2992 MHz

Can someone help me a card compatible with my computer please? I have a think and give me the link http://ebay.com http://amazon.com or, if possible