andclu,Adding new ram sticks can occasionally cause this problem to occur. To verify that this is being caused by the newly added ram i suggest removing it and reverting to the original ram that was there before this one was installed.See if this returns the computer to a state where this crashing does not occur. Then you know if/or not the added ram is causing the problem. It may be a compatibility issue related to the ram that was there and the newly added one. You can also remove the original ram and try to run the computer on only the new 512 MB stick and see what happens.If the computer runs without problems when only the new ram is in it this pretty well confirms a compatibility issue. If however the computer does not run properly with the new 512 stick it could be a defective ram module. How did you determine the type of ram and the amount that could be added to your computer?truenorth