To test NTP
Install ntp-4.2.6p5@spider-man-2-win32-setup and ntp-time-server-monitor-104 files.
Start the NTP service in the NTP Time Server Monitor application

Go to Switch and add:

ntp logging
ntp source FastEthernet0/24 ; the port source where the NTP is going to be updated
ntp server a.b.c.d ; where a.b.c.d is the IP 

It may take some minutes to update the clock, if not use:

show ntp status
show ntp associate detail

or do a debug:

logging console
conf t
terminal monitor ; this in case you are connected to the switch through VTY
debug ntp core

See the log to see what may be happening