I recently bought a Compaq Presario 2100 laptop and I bought a 512 MB of RAM. The RAM I bought was PNY DDR333 Optima Memory and I checked with the manufacturer and it is completely compatible with my laptop. I tried to install the memory and when I went to boot up my computer a screen popped up saying that Windows failed to load. Is there a certain spot I need to put the new memory in because there are two slots. The original RAM is 256 MB. If anyone can help that would be awesome!!!