I have two operating systems (win xp &win 98se),I like to know how to jump from winxp to win 98se ,is there any software which can link both

Yes, it's very easy. You shouldn't need any extra software, Windows should do it for you. Take a look here - http://www.microsoft.com/windowsxp/using/setup/learnmore/multiboot.mspx . Page 4 will be the most useful to you. I think it will just be a case of installing Win XP again (XP needs to be installed after 98 for the dual boot to work).

If this doesn't make sense, post again and we'll try to help you through it.

I have two operating systems (win xp &win 98se),I like to know how to jump from winxp to win 98se ,is there any software which can link both

Depends on what you mean by "jump" and "link". You have to reboot to load a different OS. You will need to partition if you want to access some things under both.