Need to scrub hard drive

Question

i have an older HP pentium 2 computer, it runs on windows 98. it has an aftermarket western digital hard drive. when i got this computer it wouldn't boot up and still won't. i got a little more info on this computer and in the past it has had some viruses and in my mind the best way to deal with this situation is to scrub the drive and re-install windows 98 to start from scratch. but my problem is that it won't boot up so i have no way to scrub the drive. what should i do?