If you have the ME O/S install cd, you should be able to upgrade over the
top of the existing O/S and all other applications on the machine and it
will lay down the O/S and not destroy anything.
If you have been applying SP(s) to the machine, you will need to apply
them again.
You may also want to search Google on securing IE and OE. Some people say
dump them both, but I have never had a security issue with them.