See the link in my signature. Read the Clean Boot and Security articles. Set
up a Clean Boot and clean out TEMP, TIFs, then scandisk and defrag. Then
check out the security article and go through the paces to see if it isn't
malware (spyware, etc.) clogging up your system. Should help. Outside of
that, it becomes a question of what's running in the background, what
antivirus you're using, etc. Note that I need to update that Security
article to recommend Avast Antivirus for Win98 systems, not ETrust. Avast is
free and excellent.

1.  Remove junk files -- anything you will never
need again, Temporary Internet Files (history),
DEL C:\TEMP\*.*
DEL C:\WINDOWS\TEMP\*.*
Data files you might want to reread but never
alter can be transferred to CD.
Uninstal software packages you never use.

2.  Then, use SCANDISK to be sure your hard drives
are in good working order.  For the long term, you
may find a better utility on the manufacturer's
web site.  Hard drives nowadays last for years
but not for ever.

3.  When you encounter problems (slow loading
or crashes) keep a written record of what is running
at the time (listed via Ctl Alt Del.)  You may find out
which programs need to be repaired or reinstalled.

3b.  Have a look at the Systray (right end of the
bottom bar of the Desktop) to be sure you do not
load at boot any utility you do not actually use.
These can be  summarily removed by deleting
their LiNK icons from
C:\Windows\Start Menu\Programs\Startup.

4.  When your software is in better shape (and
the junk deleted) run DEFRAG (overnight) to
rewrite your C: drive for more speed.

5.  But reliability (not crashing) is yet more important.
Win98 experts generally recommend reinstalling
the Windows operating system afresh every couple
of years.  This may require reloading patches,
updates and bug fixes as well, and reinstalling
your major software apps.  The Registry can get
cluttered over the years, and rebuilding it from
scratch may be worth the extra effort.

1.  Make certain your computer is free from viruses/spyware/trojans
per the links in the other replies.

2.  Clean up your temporary files and temporary internet files as
others have said.  Then defragment the hard drive.

3.  Clean up your startup items.  Use Start - Run - MSCONFIG  and go
to the Startup tab.  Compare the list of items that are loading at
startup with the following checklist web sites to see what can be
safely dispensed with:

http://www2.whidbey.com/djdenham/Uncheck.htm
http://www.pacs-portal.co.uk/startup_content.php
http://www.3feetunder.com/krick/startup/list.html - has trojan related
items listed

Note:  Please ensure that you fully understand the purpose of a
startup item, how and why it was put into the startup, and the
consequences (if any) of removing it before you make any changes. Some
items are very important for the proper and safe functioning of your
computer, including at least one item that is listed twice.

Disabling an item by unchecking it in MSCONFIG should only be done for
testing purposes or as a "last resort" when no other way of getting
rid of the unwanted item can be found.

4.  If the computer is still sluggish after completing all of the
above then you may need to add more RAM.   Use the System Monitor
utility that comes with Windows and use Edit - Add to set it to track
"Memory manager: Swap file in use" for several days of normal to heavy
usage.  If "Swap file in use" regularly shows as 20 mb or more then
the swap file is being used extensively and more memory would result
in improved performance.  Otherwise it is not likely to make any
noticeable difference.

This applies regardless of how much or how little RAM is currently
installed in the computer.

There is a configuration setting that needs to be entered if you are
going above 512 mb of RAM with Windows 95/98/Me and there are possible
hardware related problems that can occur with more than 1 gb of RAM
with these Windows versions.

5.  And if things are still not going well then you need to look for
specific programs that can kill the performance of a computer.  Top of
the list for this are Norton and McAfee antivirus products, and also
software firewalls such as Zone Alarm.  You may need to look for an
alternative antivirus program such as AVG or Avast and or to purchase
a router so as to allow you to run safely without a software firewall.

Good luck

Ron Martell     Duncan B.C.    Canada