richard -
If you installed W2k as a separately bootable OS and are able to boot
either W2k or W98, then you can simply erase the W2k system directory,
modify the boot.ini file appropriately (remove the line(s) that point to
W2k), and your machine will boot only to W98. You need do nothing more.
Boot.ini is a hidden/readonly/system file in %systemroot% directory,
usually c:\.
If you upgraded your existing W98 to the eval W2k OS, there's no simple
way I'm aware of to remove W2k and restore W98 as it was before. You'll
have to reinstall W98 from scratch.
By the way, if you did upgrade W98 to W2k, and W2k is misbehaving,
that's fairly common with upgrades (as opposed to clean W2k installs.)
The reason is that often systems being upgraded will contain slight
corruptions and errors, which are propagated during the upgrade to the
new system. Upgrades tend to assume that the upgrade-from system is
perfect in every respect, and just the way you want it, and unless
there's some horrendous showstopper situation will blindly use the old
settings, including registry stuff. It's only later, when the new system
starts throwing up all over your desk, that you'll discover it's a
little shaky. W2k and the other NT-class systems are especially
demanding that things be correct. Clean installs, especially from
DOS-class systems like W9x, are almost always worth the "extra" effort.