With the command prompt as administrator:
To block the pings, use this command:
netsh advfirewall firewall add rule name=”ICMP V4″ protocol=icmpv4:any,any dir=in action=block
To allow the ping again, use this command:
netsh advfirewall firewall add rule name=”ICMP V4″ protocol=icmpv4:any,any dir=in action=allow
What this does is that it adds an exception/acceptance for the ICMP into Windows native firewall.
If that does not work, do it manually. There's a guide: http://www.sysprobs.com/enable-ping-reply-windows-7