Windows 7 - Windows 7 pc and laptop

I have windows 7 professional 64 bit on a desktop and 32bit on a laptop.
Both can access the internet and ping the router.
I have turned on network discovery and set both networks to home with no homegroup and both using 40/56 bit encryption.
I can't ping or find the other computer over a wireless network
Any ideas?
Thanks

Local firewall, or perhaps third party firewall or Internet Security Suite that may contain a firewall applet preventing the passing of ICMP (Ping Packets). Also double check the subnet mask, this shouldn't be an issue since it is generally produced as part of the DCHP package you get from your router. Just a couple thoughts. Let us know how you're progressing.

Iv tried turning the firewalls off on both. No third party firewalls or anything. Pretty much clean install apart from a few apps like office, firefox msn etc
Your refering to the sharing part of the wireless adapter by ISS? if so thats not enabled. The message i get when trying to ping is

Reply from <own ip>: Destination host unreachable.

Am I understanding your issue correctly? Neither Windows 7 machine can ping the other, but both can ping the router?
No I wasn't talking about sharing, not even sure what ISS is unless you meant ICS and I wasn't talking about that either just talking about DHCP and subnet masking, but disregard, I didn't at the time nor do I now suspect that that is your problem. If you would please confirm my question in the first sentence of this post.
Thanks
Randy

Sorry about the slow reply. Yes, both machines can ping the router, but neither can ping each other.
Both the workgroups are the default 'WORKGROUP'

Sorry also for slow reply, tis the season....
Well, if both computers are working fine independent of each other and your only issue is inside the lan...if the computers can't ping each other then their almost certainly not going to be able to see or share with each other. Is it possible that the router itself is doing some sort of IP filtering? Again, check .... from command prompt type ipconfig /all make sure both machines have an ip addressing scheme consistent as to support local area networking and please make sure the actual ip address, physical address and host name are not identical.

Through ipconfig, they both have the same subnet mask (255.255.255.0) and are 192.168.172.xxx

I tried plugging my laptop in through a wired connection and I was able to ping and see it from my PC, so it must be a wireless problem somewhere :S

Nice catch....so probably the next step would be to identify the Wireless NIC and see if either the Laptop Manufacturer or the actual wireless adapter manufacturer has new drivers supporting Windows 7