don't worry,
it's normal. Windows will use most of your RAM and will allocate it's internal buffers depending on how much RAM you have. So adding more RAM will still result in about 40 -60% free RAM.
Having said that, some things can be cleaned up to clear up some unnecessary usage. Icons, and stuff takes up minimum space so don't worry.
For starters, concentrate on things in the start menu, because loading programs on start up will use up your memory, especially if you do not use it.
In Win98
start->run->msconfig
This program allows you to add and delete things on start up. In the start up tab, remove the stuff you do not need (do not remove stuff you are not sure of).
Tips:
Things like realtray, winamp, gator, schedulingagent, can be removed to increase performance (you may not have these programs).
Anyway the tip is stuff you don't use often can be removed (especially stuff produced by software from the net).
There are software (freeware) like tweakall which allows you to free memory, but they are only useful if you are really running low on Ram and is a temporary solution.