Windows 7: No proper visibility on network

I have Belkin N1 vision and connected to it by ethernet a Windows 7 (64bit) PC, and also connected by ethernet an XP (SP3) machine. I also have wireless connections for a Windows 7 (64bit) laptop and an XP (SP3) laptop.
Problem has been from day 1:
Windows 7 desktop (ethernet) only sees all other devices on network as media devices.
I have ensured the following:
All machines belong to same named workgroup.
Windows 7 machine is set to work network (as opposed to homegroup)
File sharing is enabled on all machines.
No firewall software running on any of the machines.
Have tried disabling AV software - no help.

The Windows 7 desktop is not visible at all on the network to any other machines. However, all 3 other machines DO see each other.

What is strange is that if I reboot the router then everything is fine - the Windows 7 desktop sees the other devices as computers. However, when the Windows 7 desktop has rebooted - back to square one, and it only sees media devices. Pinging works fine - machines see each other ok.

I'm now officially stumped. Anyone else had this?

Have you tried to update the firmware on your Belkin router yet?

There is also a good chance that your anti virus or firewall is causing the problem, sometimes uninstalling them is the only way to fix it. Try uninstalling the A/V software on the Win 7 machine and see if it helps.

I looked for updated firmware, but there is only BETA released - no approved firmware yet.

Well Chev65 - I uninstalled and reinstalled my AV, and now everything is fine! Thank you SO much for your help. This has been driving me mad for weeks now. I can't believe Bullguard make such crappy AV that could do this to my network.

Yes I've seen these types of problems many times and there is usually an A/V involved somehow.

It's best to set up sharing and make sure it's all working then install the A/V to see if anything changes.
Often times when you reinstall the A/V it will pick up the network and allow for sharing automatically like Bullguard seems to have done which is good.

I'm glad you got have it working again Algoz66, I'll mark this as solved.