Networking Win98 and XP PC's

We are starting to buy XP PC's but the majority of our network is still running Win98. We have our C drives shared on the Win98 network but you have to enter a password to have full access to the C drive. How do you do this on a XP PC? I'm wanting to do this just like our Win98 PC's and I see where you can share the C drive in XP but not where you have to enter a password to gain access to the C drive.

Please help....Thanks....Mark