files slow to load

I have a new computer running Windows XP SP3 that used to open data
files (.xls, .pdf, .gif, etc.) very crisply. Then I began experiencing a
noticeable delay after left-clicking these kinds of files, or right-clicking
and waiting for the menu to appear. (Executeable files run without delay.)
I determined that this delay began after networking an old windows 98 machine
with this computer. I also discovered that when the windows 98 machine is
turned on, the delay is eliminated and the XP machine works as it did before
I set up the network. As soon as I turn off the windows 98 machine, file
loading on the XP machine slows down again. I also have another XP machine
networked in this same workgroup, but I do not experirence this problem with
that machine.

I have gone through my folders to make sure I have no shortcuts, mapped
drives or anything else pointing to the Windows 98 machine. I have renamed
the workgroup and made it different from the workgroup name on the 98
machine. I have checked other network and IP settings and cannot determine
why I need to have the windows 98 machine on and connected in order for my
new windows xp machine to open data files as fast as the PC should.

I want to dispose of the Windows 98 machine, but am reluctant to do so until
I know how to fix this problem. Any ideas out there? Is there a way to
"reset" my computer to go back to the way it was before I set up the network?

Paul