Sharing Files and folders

i have 20 computers in a network with windows xp professional and al other 15 are all on win98 the whole network is on workgroup. ive got files and folders on the windows xp pro that i want to share with other windows xp pro machines but i dont want any other windows 98 pcs to look or even change the files as they are very confidential. is there a way i can share the folder and then have user rights on the folder. Kindly let me know as the soonest