Am trying to install a 128mb ram in the second slot, but when i restart the screen goes blue with error message "Dumping physical memory to hard disk"
what am i doing wrong?

That information is a little thin to base any opinion on, care to provide us with a little more information, like the make and model of your rig, the make and model of the RAM that you are trying to use.

If your using a module that's only 128MB I'm guessing that you are using an older computer, like PC100 OR PC133?

if you get the blue screen of the death, or this specific one, it's either your ram that's damaged or it's your memory slot.

normally BSOD (blue screen of death), relates to a graphics card or a RAM issue, so please can you tell us the make and type of RAM you have please!
(i have experienced many BSOD, too many to count! :D)