A definition of System Resources that is universally accepted is hard to come by.

Some computer experts argue that just about everything the computer uses - from RAM to interrupt requests, which negotiate communications between various components within the computer and its central processing unit - should be included under the System Resources rubric.

But that is way too broad a definition, at least as far as most computer people are concerned.

So let's try to follow the bouncing ball . . .

When Windows boots up, it creates three forms of temporary memory that it uses to help it with its work.

One of those temporary memory pockets is the Graphical Display Interface, also known as GDI. The GDI is a card-carrying System Resource.

Windows uses the GDI to manage and keep track of the tools that create the things you see on the screen - everything from individual letters to icons to photos.

Another form of temporary memory is called User Resources. As the name implies, Windows plays with User Resources to deal with applications running and windows open during the course of a computing session.

As far as the strict constructionists are concerned, User Resources is the other part of System Resources.

Although Windows creates these temporary memory pockets, it cannot make them infinitely big.

Thus, as you run more and more graphics-dependent programs, or decorate your monitor with heavy-duty decorations - really fanciful wallpaper, among them - you eat up more and more of the Graphics Display Interface resources.

Open and run a lot of programs, and more and more of the User Resources get devoured.

In time, your computer runs lower and lower on System Resources. If you are lucky, you get a warning when you hit rock-bottom. If not, you get bizarre computer behavior and, most probably, a crash.

But let's not engage in panic-mongering here.

You really don't run into trouble until your Graphic Display Interface and User Resources dip below the 30 percent level. At 60 percent, 70 percent etc., your System Resources haven't begun to give you reason for concern.

Let's say, though, that you get down to 35 percent or even 30 percent. Just reboot, and give Windows a chance to create virginal System Resources.

If, for some reason, you don't want to reboot, close programs. But know that the approach may not be effective. Because many programs are sloppily coded, when you close them they leave behind references in GDI and User Resources.

You could do some extended and complicated troubleshooting to find out which programs do this sort of thing, but I doubt that the result is worth the trouble unless truly low System Resources becomes a persistent problem.

You can track how your resources are doing by running Windows' Resource Meter, which you can call up from Start/Programs/Accessories/System Tools.

If it is not there, you can install it from your Windows CD by using Windows Setup in the Add/Remove Programs section of the Control Panel.

You may hear some mavens argue that the swap file, the third form of temporary memory created by Windows on bootup, is a System Resource.

OK. Fine. Just remember that the swap file, however you define it, is a key component of Windows. It works best when your hard drive has at least 10 percent of its capacity free and the drive is kept defragmented. To get to 10 percent free space, start by deleting everything in your Temp folder, which is a subfolder of Windows -- but closing all running programs first. Also, clean out your Temporary Internet Folder, also under Windows. Finally, empty your Recycle Bin and defragment. If all that does not free up enough some space, uninstall some programs.