Memory Fragmentation problem

Hi can you help

After having the computer on for a number of hours it starts to freeze up and i get a message such as "insufficient system resources exist to complete the requested service". All i can do is complete power-off shut down the computer, then restart because the normal way has frozen. I have taked lots off but this has not cured it, i have run run different programs although it has improved it just takes longer to do the same. After hours of research it appears that i have what may be called memory fragmentation. One site said: RAM memory is where all your programs reside during the time you are using (running) them. As you open a program, or use a feature of the program, like the spell checker feature in your word-processor, the program or feature is loaded into memory. When you stop using a program's feature, or close the program all together, it should release all of the RAM memory it used while it was loaded and running, thus making that memory available for the next program that you elect to load. The problem is that many programs don't release their memory cleanly. Many programs, when closed, will leave fragments of themselves in the RAM memory. The next program that loads, even the same program you closed earlier, must be loaded in another part of the memory. Little by little, as the day goes on, and as you open and close programs, or use features of these programs, the useable (free un-fragmented) memory becomes smaller and smaller. Eventually you may see the System is dangerously low in resources message, or it may get so fragmented that it can't even display the warning message, and your computer just hangs or freezes.

It seems to suggest that although more memory will help it will not cure the problem.

Is there anything you are aware of that i can try to fix this?

Thanks for reading this

Rob