You have not given us much information to work with. What program(s) are running when the message occurs? How often does the problem occur? What programs do you have running in the background? Anyway, go here for a Microsoft discussion of the same problem in Vista.
It will do it when there are no programs running at all, In the back ground only the basic Processes are running, I have tried every thing and it just keep doing it. It will do it after about 10 min of being on. It does not matter if I am doing any thing for not.
Sounds like there is a background process running which is not fully Vista/7 compatible. I had an older program which said I don't have enough memory. If you can find the program, either stop it from running or give it admin priviledges every time it runs. Older programs cannot access enough RAM if they are not run in compatibility mode or as admin.
A dual core processor along with 4G of RAM should be plenty of processing power and processing real estate. There is definitely some process going on if the problem is "predictable" within a short time after boot.
Let's search for more clues. First, if indexing is turned on, turn it off. Then, click "Start", "All Programs", "Accessories", "System Tools", and "Resource Monitor". Watch especially the graphs and percentages for CPU and memory. They should reflect your problem and help track down the offending process(es).
Other things that might affect your problem are disk (partition) size and percentage full, fragmentation of files, and things such as that. Let us know what you find. There may be others with the same problem. Good luck, we'll be waiting.