you might also try hitting F8 before it says "Starting Windows 98" then a seletion screen will come up, and you select "command prompt only" i think its number 5. so hit "5" and then hit enter. it should look like this
<C:\>
now at the propmt, type in format c:/s
<C:\>format c:/s
it'll say, "all data will be erased blah zeh blah. hit y or enter, wutever it needs for confirmation. it'll then check disk integrity and then format your ****. after words it'll ask you to enter a name for the drive 11 characters max. Type in wutever name you like up to 11 spaces long and hit enter. then it's all done! cleaned up and ready to go! after that you will need a boot disk to install Win98SE, unless you can change the boot from C: to CDrom. But you will need to get into CMOS (BIOS) like MistaX said. if you have a Win98SE boot disk (floppy) then it'll work. just pop it in, and make sure the CD is in the drive. it should take care of everything from there and start the setup program for ya. good luck!