When your PC needs to access more data than its installed RAM can store, Windows places the overflow in a large file on the hard disk known as the swap file (often called virtual memory). Since accessing data on the disk is much slower than accessing RAM, you must optimise your swap file's settings. To get to those settings, right-click the My Computer icon on your desktop, select Properties, and click the Virtual Memory button under the Performance tab. Once there, do the following:
Check the size of the swap file. By default, Windows enlarges and shrinks the file according to its needs. If hard disk space is limited, the swap file can't expand to meet its needs, so you'll have to free up space on your disk.
You can manually set the minimum and maximum file sizes by selecting the Let me specify my own virtual memory settings button in the Virtual Memory dialogue box. Entering the same number for Minimum and Maximum will fix the file's size. This may improve system performance because Windows no longer has to adjust the file size. However, you risk a memory shortage if the file size isn't large enough.
Use the fastest hard disk. If you have more than one hard disk, place the swap file on the disk with the fastest access times. To do this, just change the setting in the 'Hard disk' field in the Virtual Memory dialogue box and reboot the system.
Defragment the hard disk. Unlike Windows 3.x, Windows 9x allows the swap file to become fragmented on the disk - that is, not stored in a single, contiguous block. In systems that make heavy use of virtual memory, this fragmentation can take a steep toll on performance.
The easiest way to defragment the swap file is to use Norton Utilities' Speed Disk utility. You can also try Windows 98's Disk Defragmenter utility (under the System Tools menu). But since Disk Defragmenter treats the swap file as immovable, you'll first have to move the swap file to a second disk or partition - using the swap file 'Hard disk' setting - then defragment the disk, and finally move the file back. If you have just one disk, check Disable virtual memory, reboot, defrag the disk, enable virtual memory, and reboot again. But beware: if your system doesn't have enough RAM to run without virtual memory, it may not boot.