98 to 98 SE...What Is Involved?

Windows 98 has worked very well for me since I bought my
computer 5 years ago. It has served me well through grad
school. Now I find however that I cannot run my PDA or any
external HDs with anything older than 98 SE...I need to
upgrade.

Can this upgrade be done without erasing my HD or is this
a major OS change? I have so much of my grad. school work
on this computer that my old Zip drive back-up is simply
not practical...thus one of the reasons I wanted to back-
up with an external HD. This external HD I thought would
also make it a lot easier to download all my important
files to a new computer I need to get in the near future
(I would still use my current computer for other purposes).

I was told by someone at Western Digital that they thought
they had gotten Windows 98 SE by simply maintaining their
updates (which I too have done but see no indication that
my OS has been upgraded during this process).

Any and all help is deeply appreciated...thank you!
-Jeff