Netwrk won't work after installing new memory

Hi,

I recently ordered new replacement memory for my Dell Dimension 4300 which I've had for about 4 years. Over the past couple of months it has been sort of sluggish so I thought replacing the old memory with new memory would fix the problem. I was not upgrading. I was just getting new 512 mgs of ramm that originally came with the system. After installing the new memory sticks, it ran perfectly except for not acknowledging my network card. When I ran my diagnostics it came back that Windows XP couldn't load my drivers for my network card and I needed to disable the Plug and Play in my bios which I tried and that didn't work either. I also got a message about the IRQ setting not being correct.. So I tried reinstalling Windows thinking that might reallocate everything and set it right again and that hasn't helped. I even bought a new ethernet card and it's still not working. Does anyone have any suggestions that I could try? I'm posting this from my mom's PC.Thanks

Patty