the ping from my cisco router is working but not from the PCs

Hi, i am having a problem with my cisco 2800 router. the ping from the router to outside (i.e google.com) is working. but the ping form the PC which is connected through the LAN is not working. the PC is receiving an IP adress from the router.
the router is connected to an HSDL modem.
this is the configuration of the router:

Building configuration...
 
Current configuration : 3550 bytes
!
version 12.3
no service pad
service tcp-keepalives-in
service tcp-keepalives-out
service timestamps debug datetime msec localtime show-timezone
service timestamps log datetime msec localtime show-timezone
service password-encryption
service sequence-numbers
!
hostname aheevaLebanon
!
boot-start-marker
boot-end-marker
!
security authentication failure rate 3 log
security passwords min-length 6
logging buffered 51200 debugging
logging console critical
enable secret 5 $1$gG9r$5GuO4A0RW9HdO5VJzoH2q1
!
clock timezone PCTime 2
clock summer-time PCTime date Mar 30 2003 3:00 Oct 26 2003 4:00
no network-clock-participate aim 0
no network-clock-participate aim 1
no aaa new-model
ip subnet-zero
no ip source-route
ip tcp synwait-time 10
!
!
ip cef
ip dhcp excluded-address 172.16.16.1 172.16.16.2
ip dhcp excluded-address 172.16.16.255 172.16.31.254
ip dhcp excluded-address 172.16.26.0 255.255.255.0
!
ip dhcp pool sdm-pool1
   import all
   network 172.16.16.0 255.255.240.0
   dns-server 205.177.180.3 77.42.130.32
   default-router 172.16.16.2
!
!
no ip bootp server
ip domain name telecomexp.com
ip name-server 205.177.180.3
ip name-server 77.42.130.32
ip ssh time-out 60
ip ssh authentication-retries 2
ip inspect name DEFAULT100 cuseeme
ip inspect name DEFAULT100 ftp
ip inspect name DEFAULT100 h323
ip inspect name DEFAULT100 netshow
ip inspect name DEFAULT100 rcmd
ip inspect name DEFAULT100 realaudio
ip inspect name DEFAULT100 rtsp
ip inspect name DEFAULT100 smtp
ip inspect name DEFAULT100 sqlnet
ip inspect name DEFAULT100 streamworks
ip inspect name DEFAULT100 tftp
ip inspect name DEFAULT100 tcp
ip inspect name DEFAULT100 udp
ip inspect name DEFAULT100 vdolive
ip inspect name DEFAULT100 icmp
ip ips po max-events 100
no ftp-server write-enable
!
!
!
!
!
!
!
!
!
!
!
!
!
!
username sof privilege 15 secret 5 $1$kLs1$o.rbWbq2k9eQcrJr3FmLN.
!
!
!
!
!
!
interface FastEthernet0/0
 description $FW_INSIDE$$ETH-LAN$$INTF-INFO-FE 0/0$
 ip address 172.16.16.2 255.255.240.0
 ip access-group 100 out
 no ip redirects
 no ip unreachables
 no ip proxy-arp
 ip route-cache flow
 duplex auto
 speed auto
 no cdp enable
 no mop enabled
!
interface FastEthernet0/1
 description $FW_OUTSIDE$$ETH-WAN$
 ip address 77.42.241.114 255.255.255.248
 ip verify unicast reverse-path
 no ip redirects
 no ip unreachables
 no ip proxy-arp
 ip route-cache flow
 duplex auto
 speed auto
 no cdp enable
 no mop enabled
!
ip default-gateway 77.42.241.113
ip classless
ip route 0.0.0.0 0.0.0.0 77.42.241.113 permanent
!
ip http server
ip http authentication local
ip http secure-server
ip nat inside source list 10 interface FastEthernet0/1 overload
ip nat inside source route-map INTERNET interface FastEthernet0/1 overload
ip nat inside source static tcp 172.16.26.203 22 77.42.241.114 2222 extendable
!
!
logging trap debugging
access-list 10 permit 10.10.10.0 0.0.0.255
access-list 100 remark auto generated by SDM firewall configuration
access-list 100 remark SDM_ACL Category=1
access-list 100 permit ip any any
access-list 111 permit ip 172.16.16.0 0.0.15.255 any
no cdp run
!
route-map INTERNET permit 10
 match ip address 111
!
!
!
!
control-plane
!
!
!
!
!
!
!
!
banner login ^CAuthorized access only!
 Disconnect IMMEDIATELY if you are not an authorized user!^C
!
line con 0
 login local
 transport output telnet
line aux 0
 login local
 transport output telnet
line vty 0 4
 privilege level 15
 login local
 transport input telnet ssh
line vty 5 15
 privilege level 15
 login local
 transport input telnet ssh
!
scheduler allocate 20000 1000
!
end

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