The file system that Windows uses is sucseptable to fragmentation. What happens is that over time, files on your hard drive will be fragmented so that they are spread over your disk in more than one place. This reduces the performance of your computer. You should use a disk defragmenter on a regular basis to fix this. The needed software is included with Windows95/98
A web browser caches a local copy of images and documents you access on the WWW to reduce download times of sites you often frequent. All these files are stored in one folder on your disk, and this can sometimes slow things down. It's a good idea to clear out this cache every so often. With Netscape, you do this in the ``Options'' menu, under ``Network Preferences'' (version 4.0 users, go to Edit ->Preferences -> Advanced).
Windows 3.1 users should think hard about upgrading to Windows95, which has much better (albeit still somewhat buggy) support for dialup Internet connections. In general, Windows 3.1 users will see poorer performance and more difficulty establishing dialup connections than Windows95 users.
Windows users should check Microsoft's web site regularly to download and apply service packs to upgrade various components. From time-to-time, Microsoft releases these service packs to fix bugs and update the operating system. For example, there has already been at least one upgrade to the Windows 95 networking software that fixed quite a nasty bug.
You can reach their download area at:
http://support.microsoft.com/support/downloads/
If you have an older computer, chances are you could benefit from an upgrade of your I/O (Input/Output) chip. Older computers came with an I/O chip that tends to lose data, especially if you are using a fast modem. Cards with updated I/O chips are available for cheap prices.
A whole new computer altogether can obviously give large benefits. Newer and faster computers equal much improved performance for displaying graphics and handling data transfer.