With Windows 98, you'll probably need a boot disk. This would be a floppy with all the startup files. If you don't have one of these, you can download one from
http://www.bootdisk.com.
Once you have the disk made, you need to insert it and then turn your computer on. It will boot you through a bunch of writing on a black screen, until it gets to a C:\
From there you can re-install windows from the CD. Follow these steps to do the install.
[B]How to Install Windows 98[B\]
Insert the Windows 98 Startup disk in the floppy disk drive, and then restart your computer.
When the Windows 98 Startup menu is displayed, choose the Start computer with CD-ROM support option, and then press ENTER.
If CD-ROM support is provided by the generic drivers on the Startup disk, you receive one of the following messages, where X is the drive letter that is assigned to your CD-ROM drive:
Drive X: = Driver MSCD001
Drive X: = Driver OEMCD001
Insert the Windows 98 CD-ROM in the CD-ROM drive, type the following command at a command prompt, and then press ENTER
X:\setup
where X is the drive letter that is assigned to your CD-ROM drive.
When you receive the following message, press ENTER, and then follow the instructions on the screen to complete the Setup procedure:
Please wait while the Setup initializes. Setup is now going to perform a routine check on your system. To continue press Enter.