My friend got this old desktop computer Dimension XPS P200s that was using Win98. Suddenly he wants to upgrade it to Win98SE to install it for more convinience. So, he was using the Win98SE CD and upgrade it without have to format his hard drive. It took a while, but at last it was finished and now he's using Win98SE witout losing his old file. So, probably you can try to upgrade it instead of formatting it.