I put a used hard drive in my computer,and tried to install windows 98 it keeps saying that the drive is dirty and it needs cleaning,How do I do that?

You cannot clean a hard drive. Can you paste the exact text of the error message?

Free Software called DBAN (http://dban.sourceforge.net/)
You can download and ISO (CD image) that u can burn to a CD to create a bootable CD. From this software you can WIPE a drive, IE Overwrite all the data stored on it.

For you I would recommend a simple wipe, IE writing ZEROs to the DISC.

I agree with Rick - that is not a typical DOS or Windows error message. Knowing the exact error message would help us in offering solutions.

Are you installing from a bootup floppy?what are you typing to try to reinstall Win98?what hard drive are you installing?download the hard drive utility program from that manufacturer and try their reformatting program... you may need to do a low level format instead of the more quick 1... good luck