Windows 7 desktop cannot detect shared folders from notebooks

So I've been searching everywhere trying to find a solution to this problem, but to no avail; I really need your help!

Heres a brief of my setup.
Windows 7 x64 Professional desktop plugged into a DIR-655 wireless router.
The following computers are connected wirelessly:
- Windows 7 x32 Professional notebook
- Windows 7 x32 Starter netbook
- Snow Leopard 10.6.4 Macbook Pro
I'm using AVG anti-virus on all the Windows PC.

I have the following Advanced Sharing Settings turned on:
- network discovery
- file/printer sharing
- use 128-bit encryption


Now my problem is that my main desktop PC cannot detect shared folders in the Explorer Window's NETWORK panel. However, it can periodically detect my notebook in the other room, but it sometimes disappears as well.

What's weird is that my netbook and notebook have zero issues detecting all the shared folder computers under the Explorer Window's NETWORK panel. On my Macbook, I can also access all the Windows shared folders without any problems. I am just having trouble detecting computers on my desktop PC.

All the computers have static IPs and their homegroup named as WORKGROUP. I've already tried uninstalling my anti-virus and resetting my firewall settings to default. I can access the other computer's shared folders via their UNC name (\\computer's ip\folder name) in the Explorer Window, so I am clueless as to what the problem may be that is preventing it to auto detect NETWORK shared folders.

Could someone also explain to me the point of HOMEGROUP is when NETWORK under Explorer Window shows the same thing?


Thanks, in advance!

I've always thought "Homegroup" in Windows 7, and naming each computer as part of WORKGROUP coincided with each other.

I've already disbanded all my computers from Window 7's Homegroup and I left the Workgroup name from control panel> system as WORKGROUP on all three PCs and the Macbook. Would this be considered the proper procedure of a IPv4 network connection?


[edit] Unfortunately, the above method did not work.
However, I did find the solution by mere chance. Since the problem seems to only be isolated on my desktop PC, I went ahead and looked around network settings and compared them to working settings from my netbook/notebook. What I discovered was that in network adapter settings> properties> TCP/IPv4 properties, I had manually set IP addresses in there. If I recall, they were there because it was suggested by PortForwarding.com to set up for static IP. After removing all the addresses and setting them back to "obtain automatically", all my network computers became detectable! Even though I have fixed the problem, could someone explain to me why this had worked? I have set up my wireless router to reserve specific IPs for each computer, and using that IP to fill in TCP/IPv4 properties shouldn't have created problems, right? But why did it?