installed memory and....?

if you remove the memory module again does it start ok. if it does then you have a problem with the memory or the with the memory bank being used. to test this remove the original memory stick and replace it in it's bank with the new memory stick (straight swap - this is important). do you still get a problem? if you do then you know the problem is with the memory module in which case you should be sure that you have bought the correct type of memory for your motherboard. if it does start ok then you know that there is a problem in the memory bank that you are using. this could be because the memory banks must only be used in certain combinations if you have more than two available. this can only be found by looking at the user manual for your mobo.