This sounds like a memory error. You can confirm this by taking out your new RAM, and putting your old RAM back in. If everything works with your old RAM then either your new RAM is defective or not compatible with your system.
We might be able to help you if you give us details about your old and new RAM.
Hi its 2 X 2g slots in my latop. strangely when i did the crucial.com online scan it told me that only one of the slots was open so i decided to buy another 2g of memory via the crucial website. when i opened the computer yesterday i discovered that there was actually 2 memory sticks of ram already in...could the crucial scan have been wrong? anyway be that as it may, after putting in the new one and it did'nt work i took it out again and put the old one back in but still i get the black screen. i hope someone can help.