Tried to upgrade the memory in my Inspiron 530s. It had 1GB consisting of two 512MB, replaced with 4 1GB sticks made sure they were of the right type. After replacement computer worked for 30 minutes then got blue screen. Replaced back with original RAM, computer worked fine, tried the 4GB again same result. After putting original ram back in the second time I added two sticks of 1GB for a total of 3GB ram. Computers been working fine on the 3GB. Any reason why the computer would not accept the 4GB? The book says it should.