backup for cd-rom drive

Look in add/remove programs.
If you saved the old configuration when you installed Windows over, there should be an entry for Windows previous version. Or a description to that effect. If it is there, just select remove, and it will be gone.

If it is not there, I am hesitant to provide instructions on removing the old files.
There are just too many if -then-else conditions.

Before doing anything, is the E: drive an actual logical drive? Or a virtual drive?
You should be able to tell by clicking on properties for the drive from My Computer.

If it is a logical drive, I would then browse the drive and see whats there. It may be that it is a ghost of the original machine configuration from Dell.
It might have been a hidden partition, and what ever happened to your system may have exposed the hidden partition.

If it does look like the original machine configuration, there is no harm in just leaving it there. The only way to "reclaim" the drive space would be to use a partion manager such as Partition Magic to reconfigure the drive.
Or, you could start over, and Fdisk the drive. Which would reguire you to reload everything.

Okay, you usually can't uninstall W98. The only way to uninstall is to format the hard drive.

If your system is working properly, I would just leave everything as is.

fdisk is a program that you run from DOS to setup the partitions on the hard drive.
CHANGING THE PARTITIONS WITH FDISK ERASES ALL FILES ON THE DRIVE!!!
You can also run fdisk from the run box on the programs menu.
You can do this to see what partitions are on the drive. (option 4) This will verify if there is an extra partition on the drive.

The best way to install Windows is on a clean drive.
You must backup all files that you want to keep first. This includes e-mail, address books, favorites, documents, etc.
You will need to install all drivers for your hardware.
You will need to install and re-register your other software.
Windows 98 will start you out with IE 4. So you will need to upgrade.

Between drivers, IE updates, software updates, Windows updates, you have around 50MB of files that need tobe downloaded and saved on either a Cd, or zipped onto floppies.

If you are unsure of how to go about installing Windows from scratch, and still want to do so. I suggest that you post a new question about how to install Windows 98. That way, you will get multiple answers.

Besides TechRepublic, other resource sites include;
www.aumha.org
www.onecomputerguide.com
www.drd.dyndns.org
www.windows-help.net