Question : Can browse internet but cannot see workgroup

I have business network that is connected to a Netgear router for dsl, we are also using it as a DHCP server.  Lately we have had wierd problems with our network.  Sometimes we cannot access certain computers on the network.  Sometimes we cannot even access the workgroup at all.  We have a mix of Windows 98 second editon, Windows 2000 pro, Windows xp pro machines.  I have reset the router and machines and at times it seems to fix the problem.  
Another thing, on my xp pro machine I can access shared items through my network neighborhood but cannot access the workgroup.  We are having to do repairs on the XP Pro machines and release/renews on the the other machines to obtain a gatway quite often.

Answer : Can browse internet but cannot see workgroup

won't catch the scumware, use the spyware/malware scanners for that
 and the online virii scanners have the latest dat files