So I installed Semantic Norton anti-virus on my laptop with 500Meg memory 2x256M it brought my PC to a crawl. I shopped around this was the cheapest memory I could find event cheaper than direct from crucial. After pulling out one of my 256Meg chips I upgraded with this memory waited a couple of minutes and it came up with 1.25 GIG or memory. Now the computer works just fine for surfing etc with anti-virus running. My exact model for my HP Pavilion was ZE4930-US