Yes. Often you get passes with no errors and then passes with lots of errors.

The number of the errors is unimportant. When you have 100 000 word errors in RAM then it amounts to 400KB which is a very small area really. The location of the errors and the type of test that fails is what matters.

There are two versions of memtest: memtest86 and memtest86+. You should try them both and see if the results match.

The overnight errors may also be caused by the laptop's power management kicking in at some point for example.

 

Hay i just ran memtest last night and i really have no idea how to read it.. how do i know if the ram is good or bad??? I added my system specs in the attachment.. it ran and after about 3 hours it only passed 1 and had a ton of errors.. i have to sticks of 256 installed how do i know which is bad?? and do you know where i can find a detailed discription of what i am seeing.. i am using memtest36 3.2.. thanks for your help..

 

There should be absolutely no errors.

The error line tells you what position the error occurred in (helps to find the bad stick or the memory range that you can forbid the OS to use) and the kind of test that failed (rather irrelevant, since you won't be fixing anything).