Far more statistics are available for viewing than you would ever want to put on a single screen. Most of them are too technical for the average user. (Alas, the explanations offered by the Explain button on the Add Item screen are a joke.) But a handful of statistics are useful to just about every PC user.

Kernel: Processor Usage (%). This is an excellent indicator of your PC's overall computing burden. If your CPU usage consistently runs at over 75 percent, you're overtaxing your PC. The underlying cause may be insufficient memory, too many programs running at once, or a corrupt program that won't release the CPU. In some cases adding memory will fix the problem (see below). In others you need to get a more powerful system.

If you're stuck with high CPU usage-say, because you have an older PC that uses newer, more demanding software-make sure your CPU fan and power supply fan work properly, and confirm that air flows through the case without obstruction. A CPU that is heavily burdened runs hot, and without proper cooling the chip can fail.

Kernel: Threads. Active threads are small pieces of software that occupy RAM. The right number of threads for your PC depends on the software you happen to be running. My non-networked desktop system usually has 50 to 70 active threads when Windows 98 is running with no other applications open.

Once you have a feel for what's normal for your PC, keep an eye out for sudden changes. A program that increases the number of threads when open but does not release those threads when closed may be eating up your memory-a phenomenon called a memory leak. Memory leaks were common under Windows 3.x, and the only fix was to restart your system. Leaks are much more infrequent in Windows 9x, but they still occur, most often with older 16-bit applications. In Windows 9x, you can usually release stranded threads by closing the offending application.

If a newer 32-bit program (one written for Windows 9x) continually eats up memory and leaves stranded threads, the source of trouble may very well be a corrupted file. If this is the case, you need to reinstall the application.

Memory Manager: Unused physical memory. As you'd expect, this is the amount of physical RAM that's still free for use. You may be surprised at how little RAM remains available under Windows, even when only a few applications are running. This is because Windows constantly moves data in and out of the swap file on the hard disk. The 'Unused physical memory' setting is most useful when viewed in conjunction with the following six memory statistics.

Memory Manager: Swapfile size. Windows uses a swap file (also called virtual memory) as a temporary holding area for RAM data not currently being used. This allows Windows to run more programs concurrently than would fit in the installed physical memory alone.

Swap-file size is the size of the file created by Windows on the hard disk. If your system has a limited amount of hard-disk space, you can use this statistic to balance your hard-disk storage needs against Windows' memory needs.

Memory Manager: Swapfile in use. This statistic indicates the amount of RAM data that is actually stored in the swap file at any given moment.

Memory Manager: Page faults, Page-outs. If either of these two statistics jumps to higher-than-normal levels, Windows may be relying too heavily on the swap file. If the increase coincides with sluggish performance, you need to add more physical RAM to your system.

Memory Manager: Allocated memory. This identifies the total amount of data that Windows is manipulating in memory. To determine exactly how much RAM a given program requires, subtract the 'Memory Manager: Disk cache size' value from the amount of 'Allocated memory', with and without the program running. The difference is the amount of RAM used by that program.

Memory Manager: Locked memory. Locked memory refers to the amount of data that must remain in physical RAM and can't be swapped to the hard disk. If an application forces a high percentage of data to be locked in physical RAM, other applications' performance can slow because an inordinate amount of data must be shuttled on and off the hard disk.

Memory Manager: Disk cache size. This statistic reports the amount of RAM allocated to caching hard-disk data. On systems running the original version of Windows 95 with the FAT16 file system, you may be able to rescue a few megabytes of RAM by lowering this setting.

Watch your disk cache values to determine your system's maximum cache needs. If you see more than a megabyte of difference between what your disk cache uses and its fixed maximum value-which is determined by the MaxFileCache= setting listed under [vcache] in your system.ini file-you can recover some of the wasted RAM by lowering the MaxFileCache= setting. Of course, the memory you save may not be worth the effort if your system has more than 32MB of RAM. But if you're working with 32MB of memory or less, your applications will benefit from the extra RAM.

Dial-Up Adapter: Bytes Received/Second. This is a handy indicator for checking your dial-up connection speed. System Monitor also maintains a Bytes Transmitted/Second statistic.

- Kirk Steers