well just a few remarks about this. first of all dos. it has no difference on memory seeing as dos only uses up to 1mb of memory as it still uses the old 16bit mode so it would not affect the limit of 4gb. also having 4gb must be better than 3. at least the resources of windows would be bigger because if ur system is using up the top part of the memory then it would do the same with 3gb of memory. maybe windows its self only registers 3gb but can detect all four because of this problem. if you had only three gb would it not then use some of that top gb for other resources.