"sharing" contextual menu won't appear

I am trying to set up my PC running Win98 to be accessible by another
computer via a wireless network. It has worked before but I recently
reformatted c: and now I can't get it to work.

I have selected "Client for Microsoft Networks" in the Network control panel
and checked "I want to be able to give others access to my files" in the
dialogue box. The PC asks to reboot and then looks for several files on my
Win98SE installation CD (or anywhere) and cannot find them, including
vserver.vxd and nwserver.vxd. When I restart, an error msg comes up stating
that the vserver.vxd file cannot be found and some device nmay not work
properly.

Most conspicuous is the fact that there is no "share as" option in the
contextual menu for folders.

Please tell me what step I have missed. It may be something in Windows
Setup which I have not checked but should be checked.