How do you send identical or Unfragmented IP packets?


I am having trouble with a router and looked up the vulnerability.
I'm using a Windows XP pro and connecting to my uncle's box he's using a winodows 98 plus computer where the router is connected.It's a d-link 704,And yes I tried the ping -f (which didn't work)

IF anyone could point me in the right direction here it would be great.